Publications

Nov 17, 2020

Chemo-Enzymatic Synthesis of Levoglucosenone-Derived Bi-Functional Monomer and its Ring-Opening Metathesis Polymerization in Green Solvent Cyrene™

Chemo-Enzymatic Synthesis of Levoglucosenone-Derived Bi-Functional Monomer and its Ring-Opening Metathesis Polymerization in Green Solvent Cyrene™

The quite recent, yet quickly expanding, norbornene-levoglucosenone-based monomers family was extended to include a novel bi-functional methacrylate monomer that can be readily synthesized through a chemo-enzymatic pathway. The norbornene moiety was selectively polymerized via ring-opening metathesis polymerization (ROMP) under ambient conditions where Cyrene™ was explored for the first time as a green bio-alternative organic solvent for ROMP reactions. The activity of the metathesis catalysts was finely tuned in Cyrene™, versus common and toxic solvents such as dichloromethane, resulting in highly thermostable functional polymers with Td5% up to 401 °C and Tg of −16.8 °C.

Nov 10, 2020

Synthesis and polymerization of bio-based acrylates: a review

Synthesis and polymerization of bio-based acrylates: a review

Acrylates and polyacrylates have been produced massively due to their interesting application like Plexiglas. However, the contemporary issues of fossil depletion associated to climate change have raised serious concerns. As a result, utilization of renewable sources such as lignocellulosic material and the development of greener processes have been investigated intensively. Herein, we review the preparation of competitive (meth)acrylates and the corresponding polymers made from bio-renewable sources with a specific focus on lignocellulose. While covering a few family of biosynthon to produce acrylates through different synthetic pathways, we also approach the promising properties of the resulting materials.

Oct 15, 2020

Accessing p‐Hydroxycinnamic acids: chemical synthesis, biomass recovery or engineered microbial production?

Accessing <i>p‐</i>Hydroxycinnamic acids: chemical synthesis, biomass recovery or engineered microbial production?

p‐Hydroxycinnamic acids (i.e. , p‐coumaric, ferulic, sinapic, and caffeic acids) are phenolic compounds involved inter alia in the biosynthesis pathway of lignin. These naturally occurring molecules not only exhibit numerous attractive properties, such as antioxidant, anti‐UV, and anticancer activities, but they also have been used as building blocks for the synthesis of tailored monomers and functional additives for the food/feed, cosmetic and plastics sectors. Despite their numerous high value‐added applications, the sourcing of p‐hydroxycinnamic acids is not ensured at the industrial scale except for ferulic acid, and their production cost remains too high for commodity applications. These compounds can be either chemically synthesized, extracted from lignocellulosic biomass, and recently their production through bioconversion emerged. Herein we will discuss the different strategies described in the literature to produce these valuable molecules.

Oct 03, 2020

Glucosinolates: Natural Occurrence, Biosynthesis, Accessibility, Isolation, Structures, and Biological Activities

Glucosinolates: Natural Occurrence, Biosynthesis, Accessibility, Isolation, Structures, and Biological Activities

Glucosinolates (GSLs) are secondary plant metabolites abundantly found in plant order Brassicales. GSLs are constituted by an S-β-d-glucopyrano unit anomerically connected to O-sulfated (Z)-thiohydroximate moiety. The side-chain of the O-sulfate thiohydroximate moiety, which is derived from a different amino acid, contributes to the diversity of natural GSL, with more than 130 structures identified and validated to this day. Both the structural diversity of GSL and their biological implication in plants have been biochemically studied. Although chemical syntheses of GSL have been devised to give access to these secondary metabolites, direct extraction from biomass remains the conventional method to isolate natural GSL. While intact GSLs are biologically inactive, various products, including isothiocyanates, nitriles, epithionitriles, and cyanides obtained through their hydrolysis of GSLs, exhibit many different biological activities, among which several therapeutic benefits have been suggested. This article reviews natural occurrence, accessibility via chemical, synthetic biochemical pathways of GSL, and the current methodology of extraction, purification, and characterization. Structural information, including the most recent classification of GSL, and their stability and storage conditions will also be discussed. The biological perspective will also be explored to demonstrate the importance of these prominent metabolites.

Sep 21, 2020

Expeditious and sustainable two-step synthesis of sinapoyl malate and analogues: towards non-endocrine disruptive bio-based and water-soluble bioactive compounds

Expeditious and sustainable two-step synthesis of sinapoyl malate and analogues: towards non-endocrine disruptive bio-based and water-soluble bioactive compounds

Faced with the increasing demand from both the cosmetic industries and consumers for bio-based, safe and natural skin products, sinapoyl malate, widely described for its UV protection in plants, appears to be an excellent alternative to substitute chemical filters in sunscreens. Unfortunately, the only synthetic routes described in the literature were not only tedious but also exhibit a strong negative environmental impact, thus seriously limiting the industrialization and commercialization of sinapoyl malate. Herein, a shorter and greener synthetic pathway involving Meldrum’s acid opening with unprotected naturally occurring hydroxy-acids and its subsequent Knoevenagel-Doebner condensation with biomass-derived p-hydroxybenzaldehydes was designed and developed.

This two-step procedure, whom sustainability has been assessed using green metrics (atom economy (AE), process atom economy (PAE), E-factor and LCA), is a great alternative to the already reported procedures and allows the access to sinapoyl malate and several analogs in average to good yield. The study of the anti-UV properties, stability against UV radiation, radical scavenging and antimicrobial activities of the targets revealed attractive properties as photostable UV filters, antioxidants and preservatives. Moreover, the water solubility brought by the free carboxylic acids facilitates the incorporation of these molecules in cosmetic formulations. Finally, their innocuousness toward endocrine disruption was demonstrated.

Sep 21, 2020

Grafting Nature‐Inspired and Bio‐Based Phenolic Esters onto Cellulose Nanocrystals Gives Biomaterials with Photostable Anti‐UV Properties

Grafting Nature‐Inspired and Bio‐Based Phenolic Esters onto Cellulose Nanocrystals Gives Biomaterials with Photostable Anti‐UV Properties

New nature‐inspired and plant‐derived p‐hydroxycinnamate esters and p‐hydroxycinnamate diesters provide excellent protection against UV radiation when incorporated into a matrix. Herein, we report an efficient and sustainable pathway to graft these phenolic compounds onto cellulose nanocrystals via click‐type copper‐catalyzed azide/alkyne cycloaddition (CuAAC) reaction. The successful grafting of the phenolic esters on CNC surface was evidenced by a range of chemical analyses and the degree of substitutions (DS) of the CNC were found to depend on the structure of the phenolic ester grafted. Moreover, not only aqueous suspensions of the phenolic ester‐grafted CNCs strongly absorb in both the UVA and UVB regions, but they also exhibit average to very high photostability. Their large spectrum UV‐absorbing properties and their stability upon exposure to UV are highly influenced by the structure of the phenolic ester, particularly by the extra ester group in p‐hydroxycinnamate diesters. These findings undoubtedly demonstrate that cellulose nanocrystals decorated with such plant‐derived and nature‐inspired phenolic esters are promising sustainable nanomaterials for anti‐UV applications.

Sep 01, 2020

Effect of Heat Treatment and Light Exposure on the Antioxidant Activity of Flavonoids

Effect of Heat Treatment and Light Exposure on the Antioxidant Activity of Flavonoids

The application of food processes can lead to a modification of both the structure and the activities of flavonoids. In this article, the effect of heat treatment and exposure to light on the antioxidant activity of 6 model flavonoid solutions (rutin, naringin, eriodictyol, mesquitol, luteolin, and luteolin 7-O-glucoside) was studied. The evolution of the antioxidant activity measured after heat treatment of 130 °C at 2 h and an exposure to visible light for 2 weeks is measured by the ABTS (2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) method and represented by a new parameter called ΔTEAC. The model solution of Mesquitol showed the highest increase in ΔTEAC after a heat treatment, a value of 200 mM was obtained. The increase in ΔTEAC is always greater with thermal treatment than with light exposure. Thus, temperature and light lead to different degradation pathways of the flavonoid. In vivo measurements were carried out with solutions of naringin, erodictyol, and luteolin 7-O-glucoside. Heated solutions of flavonoids do not exhibit toxicity on cells. The specific activities of superoxide dismutase and glutathione peroxide have been determined and have shown an increased impact on the potential anti-cancer of these solutions by enhancing their cellular antioxidant activity, as well as modulation of the oxidative stress.

Aug 29, 2020

A Straightforward Access to Post-Functionalizable Polymers through Ring-Opening Metathesis Polymerization of Levoglucosenone-Derived Monomers

A Straightforward Access to Post-Functionalizable Polymers through Ring-Opening Metathesis Polymerization of Levoglucosenone-Derived Monomers

Levoglucosenone (LGO) is a cellulose-derived and commercially available platform molecule that is produced at an industrial scale. LGO contains a highly reactive double bond that was used to produce two isomers of norbornene-containing LGO monomers, endo-N-LGO (1) and exo-N-LGO (2). Furthermore, Baeyer-Villiger oxidation of 1 was performed to yield a highly-valuable chiral monomer, endo-N-HBO (3). The norbornene moiety of the prepared monomers was readily polymerized by ring-opening metathesis polymerization (ROMP) in the presence of GI catalyst to access highly thermostable polymers with Td5% up to 360 °C in the case of N-LGO-based polymers and Td5% in the range of 374-380 °C when 3 was polymerized, such range of Td5% being the highest reported up-to-date for the LGO-derived polymers. The effect of monomer concentration over the polymerization process was studied and showed that 4 M solutions lead to a better monomer conversion while preserving the control over the polymer structure and reducing the environmental factor (E factor). GI was found active in the ROMP of 3 without the need of protecting the hydroxy group and thus leading to pendent hydroxy functional polymers. Furthermore, for the first time, copolymers containing both LGO and HBO reactive moieties were prepared by random copolymerization of 1 and 3.

Aug 24, 2020

Sinapic Acid Esters: Octinoxate Substitutes Combining Suitable UV Protection and Antioxidant Activity

Sinapic Acid Esters: Octinoxate Substitutes Combining Suitable UV Protection and Antioxidant Activity

In 2021, Hawaii will permanently ban the use and sale of octinoxate-based sunscreens as studies have shown serious impacts of such UV filters on the coral reef. This ban, which could be generalized to other countries, highlights the extreme need to offer alternative UV filters that are not only effective in terms of sun protection, but also healthy with regards to human health and the environment. In this context, a wide library of p-hydroxycinnamic esters deriving from naturally occurring sinapic acid has been synthesized using a Knoevenagel–Doebner condensation. The UV filtering activities as well as the antioxidant properties of these sinapic acid esters were then investigated. The results showed promising UVB protection and antioxidant efficacy. A Structure–Activity Relationship (SAR) study on the sinapic acid esters highlighted the need of a free phenol to, as expected, observe antioxidant activity, but also to obtain a higher intensity of protection. Moreover, the nature of the ester moiety also proved to be a key structural feature for the UV absorbance, as higher steric hindrance on the ester moiety leads to more active compounds. The judicious structural design of sinapic esters thus provides promising compounds combining UV protection and antioxidant activity.

Jul 07, 2020

Conservation of ultrafast photoprotective mechanisms with increasing molecular complexity in sinapoyl malate derivatives

Conservation of ultrafast photoprotective mechanisms with increasing molecular complexity in sinapoyl malate derivatives

Sinapoyl malate is a natural plant sunscreen molecule which protects leaves from harmful ultraviolet radi‐ ation. Here, the ultrafast dynamics of three sinapoyl malate derivatives, sinapoyl L‐dimethyl malate, sinapoyl L‐diethyl malate and sinapoyl L‐di‐ t ‐butyl malate, have been studied us‐ ing transient electronic absorption spectroscopy, in a dioxane and methanol solvent environment to investigate how well pre‐ served these dynamics remain with increasing molecular com‐ plexity. In all cases it was found that, upon photoexcitation, deactivation occurs via a trans‐cis isomerisation pathway within ∼ 20‐30 ps. This cis photoproduct, formed during photodeac‐ tivation, is stable and longed‐lived for all molecules in both solvents. The incredible levels of conservation of the isomerisa‐ tion pathway with increased molecular complexity demonstrate the efficacy of these molecules as ultraviolet photoprotectors, even in strongly perturbing solvents. As such, we suggest these molecules might be well‐suited for augmentations to further im‐ prove their photoprotective efficacy or chemical compatibility with other components of sunscreen mixtures, whilst conserv‐ ing their underlying photodynamic properties.

Jun 17, 2020

Exploring the photochemistry of an ethyl sinapate dimer: An attempt towards a better ultraviolet filter

Exploring the photochemistry of an ethyl sinapate dimer: An attempt towards a better ultraviolet filter

The photochemistry and photostability of a potential ultraviolet (UV) radiation filter, dehydrodiethylsinapate, with a broad absorption in the UVA region, is explored utilizing a combination of femtosecond time-resolved spectroscopy and steady-state irradiation studies. The time-resolved measurements show that this UV filter candidate undergoes excited state relaxation after UV absorption on a timescale of ~10 picoseconds, suggesting efficient relaxation. However, steady-state irradiation measurements show degradation under prolonged UV exposure. From a photochemical standpoint, this highlights the importance of considering both the ultrafast and “ultraslow” timescales when designing new potential UV filters.

Jun 10, 2020

Optimization of an ethanol/water based sinapine extraction from mustard bran using Response Surface Methodology

Optimization of an ethanol/water based sinapine extraction from mustard bran using Response Surface Methodology

This study reports an optimization of the extraction of sinapine from industrial mustard bran using an ethanol/water mixture as a green solvent. Response surface methodology was used to determine the optimal operating conditions for the extraction process. The results show that to obtain a maximum yield of sinapine, the extraction process must be carried out at 75 °C with 70% ethanol and a ratio of 10 mL/gBDM. Under these conditions, the extraction kinetics have shown that equilibrium is reached for a concentration of 8.8 ± 0.1 mg/gBDM in 30 min. The mustard bran is exhausted to 95% sinapine after two successive extractions. The selectivity of the extraction process for sinapine could be increased by 20% using an ethanol concentration of 83%, the yield of sinapine is then 8.0 ± 0.1 mg/gBDM.

Jun 02, 2020

Sustainable Straightforward Synthesis and Evaluation of the Antioxidant and Antimicrobial activity of Sinapine and Analogs

Sustainable Straightforward Synthesis and Evaluation of the Antioxidant and Antimicrobial activity of Sinapine and Analogs

Naturally occurring sinapine was successfully synthesized through a proline-mediated Knoevenagel-Doebner condensation in ethanol. This synthetic process involving bio-based syringaldehyde, Meldrum’s acid and choline chloride, offers a sustainable alternative to the existing low yield pathways. This two-step strategy gives access to sinapine in a 52% overall yield, and has been implemented to the synthesis of sinapine analogs using 4-hydroxybenzaldehyde, 3,4-dihydroxybenzaldehyde and vanillin as precursors giving target molecules with 34-61% overall isolated yields. Purity of synthetic sinapine and that of its analogs (ca. 95%) was assessed by NMR and HPLC-MS analysis. Furthermore, antioxidant and antimicrobial activities were assessed and confirmed the potential of this series of molecules.

May 06, 2020

Innovative Bio-Based Organic UV-A and Blue Light Filters from Meldrum’s Acid

Innovative Bio-Based Organic UV-A and Blue Light Filters from Meldrum’s Acid

Faced with the ban of some organic UV filters such as octinoxate or avobenzone, especially in Hawaii, it became essential to offer new alternatives that are both renewable and safe for humans and the environment. In this context, a class of bio-based molecules displaying interesting UV filter properties and great (photo)stability has been developed from Meldrum’s acid and bio-based and synthetic p-hydroxycinnamic acids, furans and pyrroles. Moreover, p-hydroxycinnamic acid-based Meldrum’s derivatives possess valuable secondary activities sought by the cosmetic industry such as antioxidant and anti-tyrosinase properties. The evaluation of the properties of mixture of judiciously chosen Meldrum’s acid derivatives highlighted the possibility to modulate secondary activity while maintaining excellent UV protection. Meldrum’s acid derivatives are not only competitive when benchmarked against organic filters currently on the market (i.e., avobenzone), but they also do not exhibit any endocrine disruption activity.

Apr 18, 2020

Sustainable Synthesis of p-Hydroxycinnamic Diacids through Proline-Mediated Knoevenagel Condensation in Ethanol: An Access to Potent Phenolic UV Filters and Radical Scavengers

Sustainable Synthesis of p-Hydroxycinnamic Diacids through Proline-Mediated Knoevenagel Condensation in Ethanol: An Access to Potent Phenolic UV Filters and Radical Scavengers

p-Hydroxycinnamic diacids are reaction intermediates of the classical Knoevenagel–Doebner condensation between malonic acid and benzaldehydes. As they are generally obtained in low yields, they remain relatively under-studied and under-exploited. Herein, we developed and optimized a sustainable synthetic procedure allowing the production of these compounds in good to high yields (60–80%) using proline as the catalyst and ethanol as the solvent. Study of their antioxidant and anti-UV activities revealed that these p-hydroxycinnamic diacids were not only potent radical scavengers but also efficient UV filters exhibiting high photostability.

Apr 01, 2020

Sustainable synthesis and polycondensation of Levoglucosenone‐Cyrene™‐based bicyclic diol monomer: an access to renewable polyesters

Sustainable synthesis and polycondensation of Levoglucosenone‐Cyrene™‐based bicyclic diol monomer: an access to renewable polyesters

The already reported low‐yielding and non‐sustainable Et3N‐mediated homocoupling of levoglucosenone (LGO) into the corresponding LGO‐Cyrene™ diketone has been revisited and greened‐up. Using methanol as both renewable solvent and catalyst and K2CO3 as safe inorganic base, significantly improved the reaction with regards to yield, purification and green aspects. LGO‐Cyrene™ was then subjected to a one‐pot H2O2‐mediated Baeyer‐Villiger oxidation/rearrangement, followed by and acidic hydrolysis to produce a novel sterically hindered bicyclic monomer, 2H‐HBO‐HBO. This diol was further polymerized in bulk with diacyl chlorides to access new promising renewable polyesters that exhibit Tg values from ‐1 to 81 °C and good thermostability (349 °C < Td50% < 406 °C).

Mar 02, 2020

e-Book editorial "From Biomass to Advanced Bio-Based Chemicals & Materials: A Multidisciplinary Perspective"

e-Book editorial

Lignocellulose is the only renewable carbon source that can help replace oil-based chemicals and materials, in the process fighting global warming. However, because of its chemical and structural complexity, lignocellulose transformation into advanced products requires a better understanding of its composition and of its architecture at different scales, as well as a combination of physical, biological, and chemical processes, in order to render this transformation efficient and economically competitive.

Tremendous efforts continue to be made toward the production of ethanol as a biofuel from various lignocellulosic feedstocks. Furthermore, recent successes have been achieved in extracting fibers to prepare composite materials that can compete with plastic fabrics.

Importantly, lignocellulose chemistry can bring to the market original and complex chemicals that can lead to new applications, in particular when exploiting aromatic molecules or oligosaccharides from lignocellulose to produce solvents, surfactants, plasticizers, functional additives for food/feed/cosmetics, drugs, monomers, and polymers. In addition to this broad range of molecular products, fibers and particles fractionated from the lignocellulosic biomass are increasingly used to elaborate bio-based composite materials.

Overall, this Research Topic aims to illustrate how complementary approaches are relevant to address questions regarding the deconstruction of lignocellulose and the processes required to turn them into valuable bio-based and renewable products. Articles are thus welcomed in the field of techniques investigating lignocellulose complexity, the different routes using chemical and/or physical processes to fractionate lignocellulose, as well as which chemicals and materials can be obtained from lignocellulose.

Feb 26, 2020

Simultaneous recovery of ferulic acid and sugars from wheat bran enzymatic hydrolysate by diananofiltration

Simultaneous recovery of ferulic acid and sugars from wheat bran enzymatic hydrolysate by diananofiltration

A new strategy for joint separation of ferulic acid (FA) and sugars from enzymatic hydrolysate of wheat bran was evaluated.

Nanofiltration membranes with molecular weight cut-off (MWCO) in the range 150-800 g mol-1 were studied. Among them, NTR7450 and NTR7470 (Hydranautics) with MWCO between 600 and 800 g mol-1 allowed ferulic acid to be retained and sugars to permeate provided operating pH was maintained at pH >7 and ideally pH 9. In this condition, the negative charge of the membranes and the full ionization of FA conjugate to allow FA retention by electrostatic effects whereas pore size is large enough to allow sugars to permeate. Retentions obtained on model hydrolysate at 10 bar were 85% for FA and 20% for xylose. When processing real hydrolysate, however, sugar retention was more than 40%. During diafiltration, pH decrease in the retentate was observed. Manual addition of concentrated NaOH did not allow to counterbalance completely this decrease and to ensure the optimal pH of 9 in the retentate.

This led to a significative increase in sugar retention, and consequently, sugar removal in the retentate reached only 56% for a diafiltration factor Vd of 4.5. These observations were supported by a diafiltration model with variable retention.

Feb 25, 2020

Biomimetic regioselective and high-yielding Cu(I)-catalyzed dimerization of sinapate esters in green solvent CyreneTM: towards sustainable antioxidant and anti-UV ingredients

Biomimetic regioselective and high-yielding Cu(I)-catalyzed dimerization of sinapate esters in green solvent Cyrene<sup>TM</sup>: towards sustainable antioxidant and anti-UV ingredients

Naturally occurring sinapic acid and its esters are anti-UV and antiradical chemicals. This work aimed at designing an industrially relevant sustainable synthetic pathway allowing their selective β-β’ dimerization to enhance their properties with a view to their use in commercial applications such as functional additives for cosmetics, plastics and food/feed.

A copper(I)-catalyzed procedure involving pyridine and O2 from air was developed and greened up using REACH-compliant bio-based solvent Cyrene™. Optimized further through a Design of Experiments, this sustainable synthetic process was successfully implemented to various sinapate esters and validated at the multigram scale. Antiradical activities of the resulting β-β’ disinapate esters were benchmarked against commercial antioxidants, whereas their UV absorbance was compared to that of a naturally anti-UV in plants and a widely used sunscreen ingredient.

Results showed that these dimers were better radical scavengers, and not only exhibited a better UV absorbance but also covered both UV-A and UV-B regions.

Feb 21, 2020 Jan 27, 2020

Chapter "Bio-based production of chemicals through metabolic engineering" in the book "Biobased Products and Industries" edited by Prof. Charis Galanakis

Chapter

Energy resources are not only one of the most central topics of our century, but also one of the most threatened. Indeed, even though fossil fuels have met the needs for many years, global reserves diminish faster than they regenerate. To address this major issue, alternatives have been found with biofuel production using microorganisms. High efficiency processes have been developed, particularly for bioethanol with productivity up to 125 g/L. However, this chapter focuses on drop-in fuel that can be used directly in current engines and obtained through metabolic engineered microorganisms. Many efforts have been made in this field and research teams were capable of producing biohydrocarbons with concentrations up to ca. 500 mg/L. Yet, these accumulation rates are still insufficient for a profitable process at the industrial scale. This chapter also discusses the bottlenecks and solutions that could allow solving current limitations.

Dec 09, 2019

First Total Synthesis of (β-5)-(β-O-4) Dihydroxytrimer and Dihydrotrimer of Coniferyl Alcohol (G): Advanced Lignin Model Compounds

First Total Synthesis of (β-5)-(β-O-4) Dihydroxytrimer and Dihydrotrimer of Coniferyl Alcohol (G): Advanced Lignin Model Compounds

To investigate lignin degradation, scientists commonly use model compounds. Unfortunately, these models are most of the time simple β-O-4 dimers and do not sufficiently mimic the wide complexity of lignin structure (i.e., aliphatic side chains and robust C-C bonds).

Herein, we present a methodology to access advanced lignin models through the first synthesis of two trimers of monolignol G—possessing side-chains and both robust β-5 bond and labile β-O-4 bond—via a chemo-enzymatic pathway. Key steps were (1) the C-C coupling via laccase-mediated oxidation, (2) the C-O coupling via a simple SN2 between a phenolate and a bromoketoester, and (3) a modified Upjohn dihydroxylation or a palladium-catalyzed hydrogenation. (β-5)-(β-O-4) dihydroxytrimer and dihydrotrimer of coniferyl alcohol (G) were obtained in good global yield, 9 and 20%, respectively, over nine steps starting from ferulic acid.

Dec 03, 2019

(S)-γ-hydroxymethyl-α,β-butenolide (aka HBO), a Valuable Chiral Synthon: Syntheses, Reactivity and Applications

(S)-γ-hydroxymethyl-α,β-butenolide (aka HBO), a Valuable Chiral Synthon: Syntheses, Reactivity and Applications

Chirality is greatly sought for pharmaceutical compounds or fragrance and flavors. (S)-γ-hydroxymethyl-α,β-butenolide, aka HBO, is a chiral (5H)-furanone providing a polarized double bond, a lactone ring and a primary alcohol as playground for synthetic chemists. This molecule has been used for forty years in a wide range of synthetic pathways to natural and/or bioactive molecules. Its own synthesis, always from biosourced product, has also significantly evolved and could be now achieved both at large scale and by applying Green Chemistry principles. This review will explore the syntheses, the reactivity and the uses of HBO.

Nov 20, 2019

Identification of microalgae biorefinery scenarios and development of mass and energy balance flowsheets

Identification of microalgae biorefinery scenarios and development of mass and energy balance flowsheets

The notion of bioeconomy is at the basis of recent European strategies aiming at conciliating economic growth and sustainability. Consequently, extensive research has been conducted on biobased solutions such as microalgae products. Numerous initiatives to commercialize microalgae have been launched but few of them were successful. Algae biofuel is the most obvious illustration with its promises as energy supply but faces many challenges to become economically competitive. Consequently, it was recently proposed to develop microalgae biorefineries for an optimal biomass valorisation, to dilute the overall costs within a wide range of products.

Herein, the energy demand for different microalgae biorefinery scenarios is investigated and critical steps identified. Each scenario is modelled using information from literature and process engineering principles. The production of lipids, proteins, methane, fertilizers and dried biomass are considered. Once defined, the scenarios are modelled and their energy inputs are discussed. We also investigate the impact of using a biobased solvent for lipid extraction instead of a conventional one. On top of that, each scenario is assessed for two cells disruption methods.

In both cases, the study starts with dewatering the growth medium of the microalgae Chlorella vulgaris (240 kg DW h−1) and ends with the recovery of the products. The results vary from 20.07 to 66.53 MJ kg-1 input DW and highlight the importance of the cell disruption method in the total energy demand. While lipid extraction presents adverse impacts on proteins extraction due to solvent recovery, proteins extraction has beneficial effects on further methane production step. Our study concludes with the comparison of microalgae biomass with soy, for proteins and lipids production, and demonstrates quantitatively that microalgae-based technologies are still inefficient compared to present alternatives.

This work provides quantitative numbers for further evaluation of microalgae projects considering the current stage of the technology.

Oct 19, 2019

Towards symmetry driven and nature inspired UV filter design

Towards symmetry driven and nature inspired UV filter design

In plants, sinapate esters offer crucial protection from the deleterious effects of ultraviolet radiation exposure. These esters are a promising foundation for designing UV filters, particularly for the UVA region (400 – 315 nm), where adequate photoprotection is currently lacking. Whilst sinapate esters are highly photostable due to a cis-trans(and vice versa) photoisomerization, the cis-isomer can display increased genotoxicity; an alarming concern for current cinnamate ester-based human sunscreens. To eliminate this potentiality, here we synthesize a sinapate ester with equivalent cis- and trans- isomers. We investigate its photostability through innovative ultrafast spectroscopy on a skin mimic, thus modelling the as close to true environment of sunscreen formulas. These studies are complemented by assessing endocrine disruption activity and antioxidant potential. We contest, from our results, that symmetrically functionalized sinapate esters may show exceptional promise as nature-inspired UV filters in next generation sunscreen formulations.

May 14, 2019

Application of Acetyl-CoA synthetase from Methanothermobacter thermautotrophicus to non-native substrates

Application of Acetyl-CoA synthetase from Methanothermobacter thermautotrophicus to non-native substrates

The substrate selectivity of the Trp416Gly mutant of Methanothermobacter thermautotrophicus acetyl-CoA synthetase (Trp416Gly MT-ACS1) was explored. The goal was to identify its substrate range, particularly for functionalized carboxylic acid substrates that would allow post-synthesis functionalization of CoA thioesters or downstream products using metathesis or Click chemistry. Relative activities were determined by in situ formation of acyl-hydroxamate iron (III) complexes. Trp416Gly MT-ACS1 showed good activities for saturated straight chain carboxylic acids from C2 to C8, for ω-alkenyl straight chain carboxylic acids from C4 to C7 and for ω-alkynyl straight chain carboxylic acids from C5 to C7. Carboxylic acids showing ≥20% conversion in screening reactions were used in preparative conversions that completely consumed the added CoASH.

May 02, 2019

Beating of hemp bast fibres: an examination of a hydro-mechanical treatment on chemical, structural, and nanomechanical property evolutions

Beating of hemp bast fibres: an examination of a hydro-mechanical treatment on chemical, structural, and nanomechanical property evolutions

In this study, a gradually increased hydro-mechanical treatments duration were applied to native hemp bast fibres with a traditional pulp and paper beating device (laboratory Valley beater). There is often a trade-off between the treatment applied to the fibres and the effect on their integrity. The multimodal analysis provided an understanding of the beating impact on the fibres at multiple scales and the experimental design made it possible to distinguish the effects of hydro- and hydro-mechanical treatment. Porosity analyses showed that beating treatment doubled the macroporosity and possibly reduced nanoporosity between the cellulose microfibrils.

The beating irregularly extracted the amorphous components known to be preferentially located in the middle lamellae and the primary cell walls rather than in the secondary walls, the overall increasing the crystallinity of cellulose from 49.3 to 59.1%, but a non-significant change in the indentation moduli of the cell wall was observed. In addition, beating treatments with two distinct mechanical severities showed a disorganization of the cellulose conformation, which significant dropped the indention moduli by 11.2 GPa and 8.4 GPa for 10 and 20 min of Valley beater hydro-mechanical treatment, respectively, compared to hydro-treated hemp fibres (16.6 GPa).

Pearson’s correlation coefficients between physicochemical features and the final indentation moduli were calculated. Strong positive correlations were highlighted between the cellulose crystallinity and rhamnose, galactose and mannose as non-cellulosic polysaccharide components of the cell wall.

Apr 19, 2019

Improvement of protein content and decrease of anti-nutritional factors in olive cake by solid-state fermentation: A way to valorize this industrial by-product in animal feed

Improvement of protein content and decrease of anti-nutritional factors in olive cake by solid-state fermentation: A way to valorize this industrial by-product in animal feed

The present work investigates the bioconversion of the olive cake (OC) generated by olive oil industries in Morocco through solid-state fermn. using selected filamentous fungi to increase its nutritional values for subsequent valorization as ruminants feed. The fungi -namely Beauveria bassiana, Fusarium flocciferum, Rhizodiscina cf. lignyota, and Aspergillus niger were cultured on OC for 15 days. Chem. compn. as well as enzymes activities were detd. Results showed (i) an increase in protein content of up to 94% for treated OC and (ii) significant (P < 0.05) decreases of phenolic compds., up to 43%, 70% and 42% for total phenolic content, total flavonoids content, and total condensed tannins, resp. Moreover, the RP-HPLC anal. of fermented OC confirmed the degrdn. of individual phenolic compds. by the strains.

These findings demonstrate that F. flocciferum and Rhizodiscina cf. lignyota are efficient enzymes producers leading to a nutritive enhancement of this byproduct.

Apr 18, 2019

Proline-Mediated Knoevenagel–Doebner Condensation in Ethanol: A Sustainable Access to p-Hydroxycinnamic Acids

Proline-Mediated Knoevenagel–Doebner Condensation in Ethanol: A Sustainable Access to p-Hydroxycinnamic Acids

Naturally occurring p-hydroxycinnamic acids were obtained in good yields (50–85%) using a pyridine/piperidine-free Knoevenagel–Doebner condensation of the corresponding p-hydroxybenzaldehydes with malonic acid in ethanol. This method uses fully renewable and cheap nontoxic reagents and solvents. By combination of a design of experiments (DoE) and a one variable at a time optimization (OVAT), the different reaction parameters were optimized in order to favor p-hydroxycinnamic acids production over that of the two other reaction byproducts, the corresponding diacid and vinylphenol.

Mar 10, 2019

Biobased flavors production Example of the dairy lactone

Biobased flavors production Example of the dairy lactone

Aromatic compounds are ubiquitous molecules responsible for the tastes and scents that surround us. As a result, their production represents a major challenge for the agri-food, cosmetics, pharmaceutical or hygiene and maintenance products industries. There are two main routes of access to these compounds: the biotechnological and the synthetic pathways. Through the example of the dairy lactone, where the different production methods developed are described (including a biobased method from sawdust), it is possible to evaluate the advantages and disadvantages of each of these pathways.

Mar 04, 2019

Preparation of renewable epoxy-amine resins with tunable thermo-mechanical properties, wettability and degradation abilities from lignocellulose- and plant oils-derived components

Preparation of renewable epoxy-amine resins with tunable thermo-mechanical properties, wettability and degradation abilities from lignocellulose- and plant oils-derived components

100% renewable triphenol - GTF - (glycerol trihydroferulate) and novel bisphenols - GDFx - (glycerol dihydroferulate) were prepared from lignocellulose-derived ferulic acid and vegetal oil components (fatty acids and glycerol) using highly selective lipase-catalyzed transesterifications. Estrogenic activity tests revealed no endocrine disruption for GDFx bisphenols. Triethyl-benzyl-ammonium chloride (TEBAC) mediated glycidylation of all epoxies afforded innocuous bio-based epoxy precursors GDFxEPO and GTF-EPO. GDFxEPO were then cured with conventional and renewable diamines, and some of them in presence of GTF-EPO. Thermo-mechanical analyses (TGA, DSC and DMA) and degradation studies in acidic aqueous solutions of the resulting epoxy-amine resins showed excellent thermal stabilities (Td5% = 282–310 °C), glass-transition temperatures (Tg) ranging from 3 to 62 °C, tunable tan α, and tunable degradability, respectively. It has been shown that the thermo-mechanical properties, wettability and degradability of these epoxy-amine resins can be finely tailored by judiciously selecting the diamine nature, the GTF-EPO content, and the fatty acid chain length.

Feb 12, 2019

Eco-friendly extraction of Sinapine from residues of mustard production

Eco-friendly extraction of Sinapine from residues of mustard production

In this study, our efforts were focused on the optimization of phenolic compounds - mainly sinapine - extraction from residues of industrial mustard production. A preliminary work was conducted to discuss the way data from Folin-Ciocalteu analytical method are reported and exploited in the literature, and to determine whether methanol can be replaced by ethanol as extracting solvent. As this first question had found a positive answer, an optimization of the extraction process on crude and pretreated industrial residue was achieved using a Response Surface Methodology (RSM). Optimal conditions obtained through this Design of Experiments (DoE) allowed the extraction of more than 10 mg/g of defatted and dried matter (aka DDM) of phenolics from defatted and dried matter, and 13 mg/g DDM of phenolics from non-pretreated matter (results expressed as equivalent of DDM).

Feb 12, 2019

Recovery of 3-hydroxypropionic acid from organic phases after reactive extraction with amines in an alcohol-type solvent

Recovery of 3-hydroxypropionic acid from organic phases after reactive extraction with amines in an alcohol-type solvent

Reactive extraction is a well-known method for the recovery of organic acids from dilute streams. The extraction through complex formation with amines is followed by its back-extraction. Their affinity for amine extractants makes their back-extraction a limiting step. The case of 3-hydroxypropionic acid is addressed here. Three methods were compared: salts additions, diluent swing and temperature swing. Mineral bases led to complete 3-HP recovery but as a salt. Diluent swing was tested using n-hexane as the anti–solvent. Results showed that increasing the n-hexane content led to a great increase of 3-HP recovery. However, high recovery yields are associated with high dilutions. The temperature was varied from 4 to 140 °C and it led to a high decrease of the acid-amine complex formation. Our thermochemical study showed an apparent heat of reaction of -25.3 kJ/mol and, at 140 °C, 78% of 3-HP can be recovered in a single step.

Dec 10, 2018

Isolation and Synthesis of One of the Most Central Cofactors in Metabolism: Coenzyme A

Isolation and Synthesis of One of the Most Central Cofactors in Metabolism: Coenzyme A

The isolation and synthesis of coenzyme A (CoA) has been an important field since this cofactor was discovered in 1947. CoA plays a central role in human metabolism and is vital in several metabolic pathways, including fatty acid transport and degradation as well as the biosynthesis of a wide variety of compounds, including fatty acids. The high cost of commercially available CoA ($2600/g with >85% purity) has motivated several research groups tofind alternatives for its production. The variety of strategies that have been investigated for CoA production can be divided in three categories: isolation from microorganisms, total chemical synthesis, and chemoenzymatic synthesis. These approaches provide access to CoA with different efficiencies. For example, direct isolation yields of∼25 mg/kg from dried yeast have been obtained. A variety of microorganisms such as Pseudomonas alkalytica, Sarcina lutea, and Brevibacterium ammoniagenes accumulate CoA in their cultures at levels ranging from 0.03 to 115 mg/mL. Total chemical synthesis yields have ranged between 25 and 54%, and chemo-enzymatic approaches have provided overall yields of ca. 73%. This review covers all published works on producing CoAin order to compare their efficiencies, scalabilities, and convenience.

Dec 05, 2018

High yielding diastereoselective syn‐dihydroxylation of protected HBO: an access to D‐(+)‐ribono‐1,4‐lactone and 5‐O‐protected analogues

A diastereoselective chemo‐enzymatic synthetic pathway to D‐(+)‐ribono‐1,4‐lactone, a versatile chiral sugar derivative widely used for the synthesis of various natural products, has been designed from cellulose‐based levoglucosenone (LGO). This route involves a sustainable Baeyer‐Villiger oxidation of LGO to produce enantiopure (S)‐γ‐hydroxymethyl‐α,β‐butenolide (HBO) that is further functionalized with various protecting groups to provide 5‐O‐protected D‐(+)‐ribono‐1,4‐lactones. The resulting 5‐O‐protected lactones then undergo a diastereoselective and high yielding syn‐dihydroxylation of the α,β‐unsaturated lactone moiety followed by a deprotection step to give D‐(+)‐ribono‐1,4‐lactone. Through this 4‐step synthetic route from LGO, D‐(+)‐ribono‐1,4‐lactone is obtained with d.r. varying from 82:18 to 97:3 and in overall yields between 32 and 41% depending on the protecting group used. Moreover, valuable synthetic intermediates 5‐O‐tert‐butyldimethylsilyl‐, 5‐O‐tert‐butyldiphenylsilyl‐ as well as 5‐O‐benzyl‐ribono‐1,4‐lactones are obtained in 3 steps from LGO in 58, 61 and 40%, respectively.

Nov 22, 2018

Ferulic acid derivatives used as biobased powders for a convenient plasticization of polylactic acid in continuous hot-melt process

Ferulic acid derivatives used as biobased powders for a convenient plasticization of polylactic acid in continuous hot-melt process

Plasticizers are additives used to soften polymers, but most of them are oily or waxy and are difficult to process in a continuous hot-melt process. The plasticizing effect of four functionalized ferulic acid derivatives designed with controlled solubility parameters was investigated upon the study of both the thermal stability and the mechanical properties of polylactic acid (PLA) blends. The synthesized powders were incorporated into PLA through a continuous hot-melt process (extrusion) allowing the derivatives to turn from crystalline to an amorphous state. Such phase transition permitted the derivatives to act as plasticizers, reaching a reduction of the Young's modulus of PLA by 40% for one of the derivatives blended at 20 wt%. Another derivative decreased the glass transition of the PLA from 56.6 °C to 26.3 °C at the same content. These works demonstrate the interest of using phase transition additives to ease the mixing of efficient plasticizers by hot-melt processing.

Nov 22, 2018

High‐Performance Bio‐Based Benzoxazines from Enzymatic Synthesis of Diphenols

This paper reports the preparation, characterization, and performance of three low viscosity fully bio‐based benzoxazine resins synthesized from bio‐based furfurylamine, paraformaldehyde, and three new enzymatic originated diphenols obtained through a sustainable and highly selective lipase‐catalyzed enzymatic process from p‐coumaric acid, and three bio‐based diols (propanediol, butanediol, and isosorbide, respectively). The enzymatic method is used for the first time, to the authors’ knowledge, to design specific diphenolic structures dedicated to the preparation of benzoxazine thermosetting resins whose precursors exhibit easy handling within a wide processing window (from room temperature up to 200 °C). The resulting cross‐linked materials present high glass transition temperature (T g > 200 °C) and inherent charring ability upon pyrolysis (≈50 wt% at 1000 °C). These results open a valuable and new pathway to develop enhanced benzoxazines and bring them new properties.

Nov 09, 2018

Enzymatic reduction of levoglucosenone by an alkene reductase (OYE 2.6): a sustainable metal- and dihydrogen-free access to the bio-based solvent Cyrene®

Enzymatic reduction of levoglucosenone by an alkene reductase (OYE 2.6): a sustainable metal- and dihydrogen-free access to the bio-based solvent Cyrene®

Levoglucosenone (LGO) has been successfully converted into the green polar aprotic solvent 2H-LGO (aka Cyrene®) through an enzymatic process involving alkene reductases: wild-type Old Yellow Enzyme 2.6 (OYE 2.6 wt.) from Pichia stipitis and its mutant (OYE 2.6 Tyr78Trp) present the best conversion rates. This enzymatic process has been optimized in order to avoid the formation of the side-product (1R,2S)-2-hydroxy-6,8-dioxabicyclo[3.2.1]octan-4-one (OH-LGO) and reach total conversion (99%). Cyrene® was then successfully isolated by continuous extraction in quantitative yield (99%).

Oct 26, 2018

Chemo-Enzymatic Synthesis of Renewable Sterically-Hindered Phenolic Antioxidants with Tunable Polarity from Lignocellulose and Vegetal Oil Components

Chemo-Enzymatic Synthesis of Renewable Sterically-Hindered Phenolic Antioxidants with Tunable Polarity from Lignocellulose and Vegetal Oil Components

Despite their great antioxidant activities, the use of natural phenols as antioxidant additives for polyolefins is limited owing to their weak thermal stability and hydrophilic character. Herein, we report a sustainable chemo-enzymatic synthesis of renewable lipophilic antioxidants specifically designed to overcome these restrictions using naturally occurring ferulic acid (found in lignocellulose) and vegetal oils (i.e., lauric, palmitic, stearic acids, and glycerol) as starting materials. A predictive Hansen and Hildebrand parameters-based approach was used to tailor the polarity of newly designed structures. A specific affinity of Candida antarctica lipase B (CAL-B) towards glycerol was demonstrated and exploited to efficiently synthesized the target compounds in yields ranging from 81 to 87%. Antiradical activity as well as radical scavenging behavior (H atom-donation, kinetics) of these new fully biobased additives were found superior to that of well-established, commercially available fossil-based antioxidants such as Irganox 1010® and Irganox 1076®. Finally, their greater thermal stabilities (302 < Td5% < 311 °C), established using thermal gravimetric analysis, combined with their high solubilities and antioxidant activities, make these novel sustainable phenolics a very attractive alternative to current fossil-based antioxidant additives in polyolefins.

Oct 25, 2018

Chemo-enzymatic synthesis and free radical polymerization of renewable acrylate monomers from cellulose-based lactones

Chemo-enzymatic synthesis and free radical polymerization of renewable acrylate monomers from cellulose-based lactones

A chemo-enzymatic pathway involving a Candida antarctica type B lipase was developed to produce (S)-γ-hydroxymethyl-α,β-butenolide methacrylate (HBO-m) and (S)-γ-hydroxymethyl-α,β-butyrolactone methacrylate (2H-HBO-m) from (S)-γ-hydroxymethyl-α,β-butyrolactone (HBO), a biobased molecule obtained from cellulose-derived levoglucosenone. The acrylated monomer was then co-polymerized through a free radical process with methacrylamide and methylene-γ-valerolactone, a green intermediate. Finally, methylene-tetrahydropyranyl (S)- γ-hydroxymethyl-α,β-butyrolactone (M-THP-2H-HBO), synthetized via α-methylenation of 2H-HBO, was copolymerized with methyl methacrylate to access copolyacrylates exhibiting high glass transition temperatures.

Oct 08, 2018

Towards an In Situ Product Recovery of bio‐based 3‐hydroxypropionic acid: influence of bioconversion broth components on membrane‐assisted reactive extraction

Towards an In Situ Product Recovery of bio‐based 3‐hydroxypropionic acid: influence of bioconversion broth components on membrane‐assisted reactive extraction

Bioconversion broths are complex media with microorganisms that convert substrates into products in the presence of salts and nitrogen sources and that may release biomolecules. This paper deals with the impact of bioconversion broth components on the membrane‐based reactive extraction of 3‐hydroxypropionic acid (3‐HP), by tri‐n‐octylamine (TOA) in n‐decanol in preparation for an in‐situ product recovery. We focus here on the influence of 3‐HP concentration (0.5 – 10 g/L), initial pH of the solution (3 – 5), presence of proteins and salts on the extraction yields and kinetics.

Oct 06, 2018

Higher Levels of Exhaled Dimethylcyclopropane in Patients with Small Intestinal Bowel Overgrowth, Periodontitis when Associated with a Medical History of Cancer

Higher Levels of Exhaled Dimethylcyclopropane in Patients with Small Intestinal Bowel Overgrowth, Periodontitis when Associated with a Medical History of Cancer

Periodontitis (PO) is associated with an increased risk of cancer. Breath test is routinely used for detection of Small Intestinal Bowel Overgrowth (SIBO). Specific Volatile Organic Compounds (VOC) may firstly enable early non-invasive detection of cancers and secondly be markers of specific bacteria.

Sep 19, 2018

Microwave-Assisted Knoevenagel-Doebner Reaction: An Efficient Method for Naturally Occurring Phenolic Acids Synthesis

Microwave-Assisted Knoevenagel-Doebner Reaction: An Efficient Method for Naturally Occurring Phenolic Acids Synthesis

The common chemical method to synthesize Phenolic Acids (PAs) involves a relatively considerable energy intake. In order to solve this issue, microwave-assisted Knoevenagel-Doebner condensations were developed. Nevertheless, these synthetic procedures prove difficult to reproduce. Herein, we developed and optimized—by using a combination of a Design of Experiment and a standard optimization approach—a reliable procedure that converts naturally occurring p-hydroxybenzaldehydes into the corresponding PAs with conversions of 86–99% and in 85–97% yields.

Sep 01, 2018

Development of potential yield loss indicators to assess the effect of seaweed farming on fish landings

Development of potential yield loss indicators to assess the effect of seaweed farming on fish landings

In recent years, several indicators have been proposed to assess the effect of human activities on ecosystems provisioning capacity. Some of these methods focus on the Net Primary Production (NPP) available for ecosystem functioning through the comparison between the Human Appropriated Net Primary Production (HANPP) and the ecosystem's initial NPP at a given reference year. While some approaches have been proposed for marine ecosystems, most of the HANPP studies focus on terrestrial systems. This study highlights the relation between the HANPP methods and the production of natural resources in marine ecosystems. The linkage between current overfishing and future fish provisioning (ecosystem service) is well known. However, less studied before, is the relation between seaweed aquaculture and fish provisioning through the marine food web. Seaweed growth requires nutrients and light that will consequently be no longer available for natural phytoplankton production. As seaweed is periodically harvested, a fraction of the ecosystem's NPP (HANPP) is no longer available for ecosystem production. The HANPP of aquaculture reduces the ecosystem carrying capacity and thus affects commercial fish stocks. Therefore, an integrative approach is proposed in this study to assess the potential effect of seaweed farming on fish landings in the Greater North Sea. Three indicators are proposed to assess the Lost Potential Yield (LPY) in fish landings: LPYB, LPYV and LPYE, accounting respectively for reduction in biomass, monetary value and eco-exergy. For these three aspects, the LPY results remains smaller than the seaweed production, meaning that the overall natural resources balance for seaweed farming is positive.

Aug 31, 2018

Detoxification of highly acidic hemicellulosic hydrolysate from wheat straw by diananofiltration with a focus on phenolic compounds

Detoxification of highly acidic hemicellulosic hydrolysate from wheat straw by diananofiltration with a focus on phenolic compounds

Nanofiltration was studied for detoxification of lignocellulose hydrolysates obtained in harsh conditions. A hemicellulosic hydrolysate obtained from sulfuric acid steam explosion of wheat straw and presenting very low pH (= 1) and high osmotic pressure (28 bar) was studied and 8 inhibitory compounds were followed, among which 4 phenolic compounds. Several polymeric nanofiltration membranes were compared for separation performances and permeabilities; DK membrane (GE Osmonics) proved suitable with high rejection of sugars (> 99%) and lower rejections of inhibitors. Acetic acid and furfural were quasi-fully transmitted whereas the rejection of compounds ranked as follow: HMF (5-hydroxymethyl-furfural) < coumaric acid < levulinic acid < vanillin < ferulic acid < syringaldehyde with values of 40%, 50%, 60%, 80%, 90% and 98%, respectively, at a permeate flux of 14 L h−1 m−2. Diafiltration was carried out at a transmembrane pressure of 26 bar until 3 DV (Diafiltration Volume) to complete detoxification, and continuous and sequential-dilution modes were compared. Thanks to the permeability of the membrane to the monovalent form of sulfuric acid HSO4-, effective transmembrane pressure was increased and pH reached 2. At 3 DV, both modes showed removal performances between 92% (acetic acid and furfural) and 25% (syringaldehyde). Irreversible fouling was observed, leading to 30% permeability loss after diafiltration.

Jun 27, 2018

Importance of mediators for lignin degradation by fungal laccase

Importance of mediators for lignin degradation by fungal laccase

Three of the major ligninolytic enzymes – lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase (LA) – as well as the secretome of a white-rot fungi – Grammothele fuligo– are tested on three industrial lignins (organosolv, alkali and Kraft), to investigate and study the differences in biodegradation reactions and mechanism of these three lignins. Strategies involving additives in laccase mediated systems were also considered to produce small phenolic compounds. Three new or underreported additives including 2,4,6-tri-tert-butylphenol (TTBP), 4-tert-butyl-2,6-di-methylphenol (TBDMP), and 3-hydroxyanthranilic acid (HAA), are compared to three classic laccase mediators violuric acid (VA), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and 1-hydroxybenzotriazole (1-HBT). Decrease of molecular weight by up to 73 % could be obtained on organosolv lignin with LA-VA systems, and 49 %, 43 % and 39 % when LA was used with ABTS, TBDMP and 1-HBT, respectively. In-depth analysis of the degradation products by quantitative 2D HMQC NMR indicated that the oxidation is mediator-dependant and provides new insights on the enzymatic mechanism.

May 08, 2018

Gas‐Solution Phase Transient Absorption Study of the Plant Sunscreen Derivative Methyl Sinapate

The plant sunscreen derivative methyl sinapate is studied in the gas‐ and solution‐phase as an important step in understanding the structure‐dynamics‐function relationship of plant sunscreens such as sinapoyl malate. Results from gas‐phase experiments suggest a three step deactivation process after photoexcitation. Photoexcitation to the S1 state results in internal vibrational energy redistribution within 3 ps. Intersystem crossing then occurs in 30 ps between S1 and T1 and the latter state then persists outside our probe window (urn:x-wiley:23670932:media:cptc201800060:cptc201800060-math-0001 1 ns). In solution with the weakly perturbing solvent cyclohexane, a dramatic change in the photophysical properties is observed. A trans‐cis isomerisation is observed to occur in 3 ps via a 1urn:x-wiley:23670932:media:cptc201800060:cptc201800060-math-0002 /S0 conical intersection. The population which does not complete the isomerisation, relaxes via vibrational energy transfer to the solvent in 9 ps. A long‐lived photoproduct is then observed to persist and is identified as the cis‐isomer.

Mar 19, 2018

Organic solvent- and catalyst-free Baeyer-Villiger oxidation of levoglucosenone and dihydrolevoglucosenone (Cyrene): a sustainable route to (S)-y-hydroxymethyl-α,β-butenolide and (S)-γ-hydroxymethyl-γ-butyrolactone

Organic solvent- and catalyst-free Baeyer-Villiger oxidation of levoglucosenone and dihydrolevoglucosenone (Cyrene): a sustainable route to (S)-y-hydroxymethyl-α,β-butenolide and (S)-γ-hydroxymethyl-γ-butyrolactone

A straightforward and sustainable route to (S)-γ-hydroxymethyl-α,β-butenolide (HBO) and (S)-γ-hydroxymethyl-α,β-butyrolactone (2H-HBO), two valuable chemical platforms for the synthesis of fine chemicals such as drugs, pheromones, flavors and fragrances, has been optimized using renewable cellulose-based levoglucosenone (LGO) and Cyrene® as starting materials and aqueous H2O2 as both a solvent and an oxidizing agent. Combined with short-path distillation, this procedure provides enantiopure HBO and 2H-HBO in yield as high as 72% at the kilo scale.

Feb 20, 2018

Enzymatic synthesis of resveratrol α-glycosides from β-cyclodextrin-resveratrol complex in water

Enzymatic synthesis of resveratrol α-glycosides from β-cyclodextrin-resveratrol complex in water

Although resveratrol (3,5,4'-trihydroxy-stilbene) is one of the most studied natural product because of its biological properties such as antioxidant or anticancer, its low water solubility and stability (influenced by pH, light and increased temperature), as well as its propensity to oligomerize, limit its bioavailability and applications in nutraceutic, cosmetics or pharmaceutical industries. Besides, resveratrol production at the multigram scale through vine cell culture is limited by the tedious extraction of pure resveratrol from the bioconversion medium due to its complexation by cyclodextrins, the latter being used as elicitors in the bioproduction process.

In this work, we have been able to overcome all these drawbacks by performing a single organic solvent-free enzymatic α-glycosylation directly from the β-cyclodextrin-resveratrol complex in water using β-cyclodextrin as glycoside-donor. The combined effects of five parameters (CGTase amount, cyclodextrin amount, cyclodextrin/resveratrol ratio, pH and temperature) were studied by design of experiments (DoE) to maximize the glycosylation yield. The optimal setting point of parameters was obtained by response surface methodology (RSM). After optimization, an efficient α-glycosylation was performed being obtained 35% of molar yield.

The major glycosides - two mono-glycosides: 3-O-α-D-glucosyl-resveratrol and 4'-O-α-D-glucosyl-resveratrol and two di-glycosides: 3-O-α-D-maltosyl-resveratrol and 4'-O-α-D-maltosyl-resveratrol - were characterized using a hyphenated liquid chromatography-solid phase extraction-nuclear magnetic resonance system, then separated and purified using Centrifugal Partition chromatography (CPC). Their antiradical properties, as well as that of their crude mixture, were evaluated through DPPH analysis. Results confirmed that the position 4'-OH is the best position for the glycosylation to maintain the highest antiradical properties.

Feb 14, 2018

Recovering ferulic acid from wheat bran enzymatic hydrolysate by a novel and non-thermal process associating weak anion-exchange and electrodialysis

Recovering ferulic acid from wheat bran enzymatic hydrolysate by a novel and non-thermal process associating weak anion-exchange and electrodialysis

Agricultural by-products such as wheat bran and straw are rich in arabinoxylans. Composed of a main chain of β-(1,4) linked xylose ramified by arabinose and ferulic acid, these polymers are sources of valuable molecules, in particular ferulic acid and monomeric (xylose, arabinose and glucose) and oligomeric carbohydrates. Enzymatic hydrolysis using hemicellulasic cocktails obtained from Thermobacillus xylanilyticus provide an eco-friendly alternative to acid or alkaline deconstruction.

In this article, downstream purification of the enzymatic hydrolysate of wheat bran with a weak anion-exchange resin (Amberlyst A21- Dow) in free-base form was studied and optimized to reach concentrated ferulate fractions in environment-friendly conditions. A demineralization step by homopolar electrodialysis prior to anion-exchange allowed most of the competing inorganic anions to be removed from the hydrolysate. The capacity of fixation of ferulic acid on the active sites of the resin was increased, as well as purity and concentration of the basic eluate, consequently.

Ferulic acid could therefore be crystallized by adjusting the pH of the eluate. 83% was crystallized and purity (NMR) reached 90-95%. At last, 52% of ferulic acid released from wheat bran by the hemicellulasic cocktail was purified and recovered as a solid. Moreover, more than 50 BV (Bed Volume) of the hydrolysate could be recovered during the resin saturation step as rather pure carbohydrates under monomeric (xylose, arabinose and glucose) and oligomeric (xylobiose, xylotriose and xylotetraose) form.

Jan 02, 2018

Investigating isomer specific photoprotection in a model plant sunscreen

Investigating isomer specific photoprotection in a model plant sunscreen

Sinapate esters are used throughout the plant kingdom, for example in photoprotection from ultraviolet radiation. Sinapate esters are naturally produced in their E-isomeric form; however, upon exposure to ultraviolet radiation, photoisomerization drives Z-isomer formation. To elucidate the photoprotection capacity of E vs. Z forms of sinapate esters, we explore the photochemistry of the model system, Z-ethyl sinapate. Following a novel Z-ethyl sinapate synthesis, we demonstrate that photoprotection is isomer independent. This suggests that, regarding photoprotection, there were no evolutionary pressures for biosynthesis of either isomer.

Dec 22, 2017

Biocatalytic Synthesis and Polymerization via ROMP of New Biobased Phenolic Monomers: A Greener Process toward Sustainable Antioxidant Polymers

Biocatalytic Synthesis and Polymerization via ROMP of New Biobased Phenolic Monomers: A Greener Process toward Sustainable Antioxidant Polymers

Antioxidant norbornene-based monomers bearing biobased sterically hindered phenols (SHP) - NDF (norbornene dihydroferulate) and NDS (norbornene dihydrosinapate) - have been successfully prepared through biocatalysis from naturally occurring ferulic and sinapic acids, respectively, in presence of Candida antarctica Lipase B (Cal-B). The ring opening metathesis polymerization (ROMP) of these monomers was investigated according to ruthenium catalyst type (GI) vs. (HGII) and monomer to catalyst molar ratio ([M]/[C]). The co-polymerization of antioxidant functionalized monomer (NDF or NDS) and non-active norbornene (N) has also been performed in order to adjust the number of SHP groups present per weight unit and tune the antioxidant activity of the copolymers. The polydispersity of the resulting copolymers was readily improved by a simple acetone wash to provide antioxidant polymers with well-defined structures. After hydrogenation with p-toluenesulfonylhydrazine (p-TSH), the radical scavenging ability of the resulting saturated polymers was evaluated using α,α-diphenyl-β-picrylhydrazyl (DPPH) analysis. Results demonstrated that polymers bearing sinapic acid SHP exhibited higher antiradical activity than the polymer bearing ferulic acid SHP. In addition it was also shown that only a small SHP content was needed in the copolymers to exhibit a potent antioxidant activity.

Oct 10, 2017

A microstructural and chemical approach to highlight how a simple methyl group affects the mechanical properties of a natural fibers composite

A microstructural and chemical approach to highlight how a simple methyl group affects the mechanical properties of a natural fibers composite

Two ferulic acid derivatives (BDF and BDF-Me) were prepared using chemo-enzymatic synthesis and used as additives for the pretreatment of hemp fibers. Incorporation of these fibers into a polycaprolactone matrix by hot-melt extrusion process aimed to improve the dispersion of the fibers and the mechanical properties of the resulting materials. Young's modulus and tensile strength of the composites were investigated at the micrometer scale by chemical imaging. The very simple methylation of the phenolic functions led to significant mechanical properties differences due to the dispersion of the fibers caused by a plasticizing effect of the ferulic acid derivative. This significant plasticizing effect of BDF-Me is observed at a content as low as 0.8 w% and opens the way for synthesizing a new family of biobased plasticizers involving transition from crystal state to amorphous phase.

Aug 24, 2017

Isocyanate-free synthesis and characterization of renewable poly(hydroxy)urethanes from syringaresinol

Isocyanate-free synthesis and characterization of renewable poly(hydroxy)urethanes from syringaresinol

In a context of replacement of petro-sourced and toxic bisphenol-A (BPA), syringaresinol, a naturally occurring bisphenol deriving from sinapic acid, has been proposed as a greener and safer alternative. This work focuses on its applications for Non-Isocyanate PolyUrethanes (NIPUs) synthesis. A five-membered cyclic carbonate SYR-CC has been prepared by carbon dioxide addition to bis-epoxy monomer SYR-EPO derived from syringaresinol. Upon polyaddition of SYR-CC with different biosourced and petrosourced diamines, the resulting polyhydroxyurethanes were fully characterized by structural analyses (FT-IR, 1H NMR, HPLC-SEC), and thermal analyses (TGA, DSC). These thermoplastics displayed high molar mass ((Mn) ̅ = 5.4 kg.mol-1), excellent thermal stabilities (Td5% = 267-281 °C) and glass transition temperatures (Tg) ranging from 63 to 98 °C. Complementary, the coupling of SYR-CC with a triamine gave a thermoset material with interesting Tg (62 °C) and high thermal stability (Td5% = 225 °C).

Aug 05, 2017

Mechanistic modeling and equilibrium prediction of the reactive extraction of organic acids with amines: a comparative study of two complexation-solvation models using 3-hydroxypropionic acid

Mechanistic modeling and equilibrium prediction of the reactive extraction of organic acids with amines: a comparative study of two complexation-solvation models using 3-hydroxypropionic acid

A comprehensive study of equilibrium states involved in the reactive extraction of 3-hydroxypropionic acid (3-HP) by tri-n-octylamine (TOA) in n-decanol is described. Complexation phenomena between 3-HP and TOA were revealed by infrared spectroscopy (FT-IR). This study demonstrated that the main extraction mechanism is the formation of an ion pair involving the dissociated form of 3-HP.

Chemical models were then formulated, taking the formation of the ion pair between 3-HP and TOA and the influence of the amount of solvent in the organic phase into account. Two models are proposed: (1) a stoichiometric model where the solvent is seen as a reagent that is involved in the complexation as a synergistic extractant, but with competition for solvation via H-bond interactions with TOA; (2) a model where the solvent is seen as a phase modifier that improves the physicochemical properties of the extractant and that changes the complexation equilibrium. Both models describe the extraction yields in the investigated ranges, with Model (2) being particularly predictive since it provides a mean absolute prediction error of less than 2% in yield units. According to this latter model, the complexation equilibrium coefficient increases with the increase of the n-decanol proportion in the organic phase. Model (2) shows that solvation effects are better described as non-stoichiometric interactions.

Therefore, the two mechanistic models accurately represent extraction yields over a wide range of initial conditions and are potentially transposable to other reactive extraction systems. Such knowledge is essential for further implementation of downstream processes.

Jul 11, 2017

Lignocellulosic fibers: a critical review of the extrusion process for enhancement of the properties of natural fiber composites

Lignocellulosic fibers: a critical review of the extrusion process for enhancement of the properties of natural fiber composites

Natural fiber composites have various applications, since they can bring interesting mechanical and sustainability properties. Extrusion with a single- or twin-screw is the main industrial process to incorporate lignocellulosic fibers into polymers. In this review, the origin and preparation of lignocellulosic fibers are first presented, before discussing the composite processing, with a particular emphasis on the impact of process conditions on the composites final properties that is highly related to the final application. A broad panel of composites reinforced with lignocellulosic fibers is reviewed along with their polymeric matrix, lignocellulosic fiber type and pretreatments, and extrusion process conditions. Finally, the most critical extrusion process parameters (screw profile, speed and temperature) are also examined in order to determine some guidelines to optimize lignocellulosic fiber composites preparation.

Jul 10, 2017

Elucidating nuclear motions in a plant sunscreen during photoisomerization through solvent viscosity effects

Elucidating nuclear motions in a plant sunscreen during photoisomerization through solvent viscosity effects

We explore the effects of solvent viscosity on trans-cis photoisomerization of sinapoyl malate, which is utilized as a sunscreen molecule in plants. Our results demonstrate that viscosity has a signifcant effect on the timescale for isomerization, providing insight into the nuclear motions involved. The ramifications of these finding are discussed with reference to sinapoyl malate’s in vivo photoprotection properties.

Jul 06, 2017

Wheat and Sugar Beet Coproducts for the Bioproduction of 3-Hydroxypropionic Acid by Lactobacillus reuteri DSM17938

Wheat and Sugar Beet Coproducts for the Bioproduction of 3-Hydroxypropionic Acid by <i>Lactobacillus reuteri</i>  DSM17938

An experimental design based on Response Surface Methodology (RSM) was used for the formulation of a growth medium based on sugar beet and wheat processing coproducts adapted to the cultivation of Lactobacillus reuteri (L. reuteri) DSM17938. The strain was cultivated on 30 different media varying by the proportions of sugar beet and wheat processing coproducts, and the concentration of yeast extract, tween 80 and vitamin B12. The media were used in a two-step process consisting of L. reuteri cultivation followed by the bioconversion of glycerol into 3-hydroxypropionic acid by resting cells. The efficiency of the formulations was evaluated according to the maximal optical density at the end of the growth phase (ΔOD620nm) and the ability of the resting cells to convert glycerol into 3-hydroxypropionic acid, a platform molecule of interest for the plastic industry. De Man, Rogosa, and Sharpe medium (MRS), commonly used for the cultivation of lactic bacteria, was used as the control medium. The optimized formulation allowed increasing the 3-HP production.

May 16, 2017

A novel and integrative process: From enzymatic fractionation of wheat bran with a hemicellulasic cocktail to the recovery of ferulic acid by weak anion exchange resin

A novel and integrative process: From enzymatic fractionation of wheat bran with a hemicellulasic cocktail to the recovery of ferulic acid by weak anion exchange resin

An integrated and eco-friendly process including enzymatic hydrolysis with a hemicellulasic cocktail and a chromatographic purification step was developed to obtain ferulic acid from wheat bran. Thermobacillus xylanilyticus, a thermophilic and hemicellulolytic bacterium, was able to produce enzymatic cocktails containing xylanase, xylosidase, arabinosidase and esterase activities. The cocktails produced were used to deconstruct destarched wheat bran, allowing the release of 6%, 20% and 37% (w/w) of monomeric arabinose, xylose and ferulic acid, respectively. A weak anionic resin under free-base form was proved successful to separate the carbohydrate fraction from the ferulate one after acidification. Ferulate was recovered at high concentration (15 g/L) during regeneration of the resin. This non-optimized purification step allowed recovering 67% of ferulic acid fixed on the resin. Global recovery of ferulic acid contained in wheat bran after both enzymatic fractionation and purification stages reached 21.8%.

Apr 18, 2017

Conversion of Glycerol to 3-Hydroxypropanoic Acid by Genetically Engineered Bacillus subtilis

Conversion of Glycerol to 3-Hydroxypropanoic Acid by Genetically Engineered <i>Bacillus subtilis</i>

3-Hydroxypropanoic acid (3-HP) is an important biomass-derivable platform chemical that can be converted into a number of industrially relevant compounds. There have been several attempts to produce 3-HP from renewable sources in cell factories, focusing mainly on Escherichia coli, Klebsiella pneumoniae, and Saccharomyces cerevisiae. Despite the significant progress made in this field, commercially exploitable large-scale production of 3-HP in microbial strains has still not been achieved. In this study, we investigated the potential of Bacillus subtilis as a microbial platform for bioconversion of glycerol into 3-HP. Our recombinant B. subtilis strains overexpress the two-step heterologous pathway containing glycerol dehydratase and aldehyde dehydrogenase from K. pneumoniae. Genetic engineering, driven by in silico optimization, and optimization of cultivation conditions resulted in a 3-HP titer of 10 g/L, in a standard batch cultivation. Our findings provide the first report of successful introduction of the biosynthetic pathway for conversion of glycerol into 3-HP in B. subtilis. With this relatively high titer in batch, and the robustness of B. subtilis in high density fermentation conditions, we expect that our production strains may constitute a solid basis for commercial production of 3-HP.

Mar 13, 2017

From bench scale to kilolab production of renewable ferulic acid-based bisphenols: optimisation and evaluation of different purification approaches towards technical feasibility and process environmental sustainability

From bench scale to kilolab production of renewable ferulic acid-based bisphenols: optimisation and evaluation of different purification approaches towards technical feasibility and process environmental sustainability

In earlier authors work, a new class of non-toxic and renewable bisphenols able to substitute bisphenol A and exhibiting potent antioxidant and antiradical activities has been prepared from ferulic acid through a chemoenzymatic pathways at bench scale. Scaling-up a process is not always trivial and straightforward. Technical feasibility of synthesis and overall process yield must be assessed. All decisions should be justified regarding technical constraints and environmental sustainability. This work is focused on the kilolab production of bis-O-dihydroferuloyl 1,4-butanediol (BDF), one of these very promising renewable bisphenols. Recrystallization and organic diananofiltration in a single stage (SSD) and two stages (TSD) were compared taking into account the previous considerations.

As result, the synthesis and purification of BDF by recrystallization were successfully scaled-up at kilolab scale, being obtained a significant improvement in the overall yield (from 63% at labscale to 84% at kilolab scale) for a purity grade of 95%. To assess the organic diananofiltration as an alternative purification method, a set of 6 commercial organic solvent resistant membranes were evaluated. Starting from a solution (1 g/L) containing 80%(w/w) of BDF and 20% (w/w) of an excess reagent (ethyl dihydroferulate, EtDFe), GMT-oNF1 membrane showed to be able to discriminate them. A two-stage membrane diafiltration (TSD) in cascade was proposed, being observed a drastic increase in the product yield (from 77% in a single stage to 95%) without compromising its final purity (95%). Since solvent recycling has a significant impact on the process sustainability, a nanofiltration step for solvent recovery was assessed, . 90% of the solvent was recovered with a level of impurities lower than 1%. Recrystallization and all filtration-based processes were compared in terms of green metrics such as mass and solvent intensity and energy consumption.

Results showed that only the integration of solvent recycling in filtration-based processes and the use of a concentrated starting solution (150 g/L instead of 1 g/L) may lead to similar magnitude values observed for recrystallization. Thus, even being a less energetic intensive process (4-fold), the TSD is still a solvent intensive process (3-fold), which is inevitably reflected in a higher environmental footprint (evaluated by LCA).

Feb 24, 2017

Towards an extractive bioconversion of 3-hydroxypropionic acid: study of inhibition phenomena

Towards an extractive bioconversion of 3-hydroxypropionic acid: study of inhibition phenomena

3-hydroxypropionic acid (3-HP) microbial synthesis through glycerol bioconversion by Lactobacillus reuteri is at the moment characterized by too low performances to consider production at industrial scale. To avoid its toxic accumulation in the medium and to recover this molecule of interest, 3-HP in situ reactive extraction from bioconversion broth was investigated using a hollow fiber membrane contactor (HFMC) in order to intensify its production. The so-called integrated system was compared with the conventional bioconversion system. The impact of the extractive bioconversion on the overall production performance and on cell physiological state was studied. Results underlined drastic inhibitory effects on the producing bacteria, especially under extractive bioconversion conditions despite the use of a HFMC supposed to avoid direct contact between organic phase and bacteria. Indeed, the extractant phase components (trioctylamine in n-decanol) were found to be toxic for the cells (due to solubility and by direct contact). These phenomena were increased by the presence of 3-hydroxypropionaldehyde (3-HPA) and 3-HP produced during glycerol bioconversion. These cumulative effects induced a complete loss of the cell membrane integrity and esterase activity after 1.5 h of extractive bioconversion. When the bioconversion was conducted alone, the bacterial inhibition was lower, as around 50% of L. reuteri cells remained active with unaltered membrane after 3 h. Hypotheses concerning the mechanisms of action of the observed inhibitions were proposed and discussed. This work highlighted the importance of performing such an integrative approach to address specific questions prior to the optimization of the whole process.

Feb 08, 2017

Ultrafast Barrierless Photoisomerization and Strong UV Absorption of Photoproducts in Plant Sunscreens

Ultrafast Barrierless Photoisomerization and Strong UV Absorption of Photoproducts in Plant Sunscreens

We study the photoprotectivemechanisms of sinapoyl malate and sinapic acid in aqueous solution by utilizing femtosecond transient absorption spectroscopy and time-dependent density functional theory.We find that excited ππ* states of the two molecules relax to the ground states via a barrierless trans-cis photoisomerizationin a few tens of picoseconds. The formation of cis-photoproducts largely reduces the efficacy of sinapic acid as a sunscreen. In contrast,the efficacy ofthe plant sunscreen sinapoyl malate is affected slightly due to the strong UVabsorption of its cis isomer.

Jan 03, 2017

Syringaresinol: a renewable and safer alternative to Bisphenol A for epoxy-amine resins

Syringaresinol: a renewable and safer alternative to Bisphenol A for epoxy-amine resins

A renewable bis-epoxy, SYR-EPO, has been prepared from syringaresinol, a naturally occurring bisphenol deriving from sinapic acid, using a chemo-enzymatic synthetic pathway. Estrogenic activity test revealed no endocrine disruption for syringaresinol. Its glycidylation afforded bis-epoxy SYR-EPO with excellent yield and purity. This biobased safer epoxy precursor was then cured with conventional and renewable diamines for the preparation of epoxy-amine resins. The resulting thermosets were thermally and mechanically characterized (TGA, DSC and DMA). Thermal analyses of these new resins showed excellent thermal stabilities (Td5% = 279-309 °C) and Tg ranging from 73 to 126 °C, almost reaching the properties of those obtained with DiGlycidylEther of Bisphenol A (DGEBA), extensively used in polymer industry (Td5% = 319 °C and Tg = 150 °C for DGEBA-IPDA resins). Degradation studies in NaOH and HCl aqueous solutions also highlighted the robustness of the syringaresinol-based resins, similar to bisphenol A (BPA). All these results undoubtedly confirmed the potential of syringaresinol as a greener and safer substitute to BPA.

Dec 16, 2016

Chemo-Enzymatic Synthesis and Characterization of Renewable Thermoplastic and Thermoset Isocyanate-Free Poly(hydroxy)urethanes from Ferulic Acid Derivatives

Chemo-Enzymatic Synthesis and Characterization of Renewable Thermoplastic and Thermoset Isocyanate-Free Poly(hydroxy)urethanes from Ferulic Acid Derivatives

This study presents the syntheses and characterization of renewable non-isocyanate polyurethanes from a new family of aromatic C5-cyclocarbonate precursors with different functionalities obtained from non-toxic ferulic acid derivatives by glycidylation and carbonation under high carbon dioxide pressure. Depending on the functionality, linear NIPU chains (thermoplastics) or cross-linked NIPU networks (thermosets) have been obtained. The thermoplastics NIPU molar masses were determined using SEC and 1H-NMR. The thermal and thermo-mechanical properties of the NIPUs were assessed by DSC, DMA (for thermosets), and TGA to determine the influence of the NIPU chemical structure on its properties. The range of Tg obtained (17 - 72 °C) was efficiently correlated with the degree of freedom and the molar mass of the NIPU repeat unit.

Dec 05, 2016

Exploring the microstructure of natural fibre composites by confocal Raman imaging and image analysis

Exploring the microstructure of natural fibre composites by confocal Raman imaging and image analysis

We describe a combination of Confocal Raman Imaging (CRI) and quantitative image analysis to characterise biocomposite material microstructures. Both techniques offer lateral resolutions close to 1.3 μm and axial resolution of 13 μm, while simplifying sample preparation to hand-cutting without any surface preparation. Extruded and injected polycaprolactone/hemp fibre composites were used as demonstration biocomposites. A green macrobisphenol additive (bis-O-dihydroferuloyl-1,4-butanediol) was also used as a chemical probe to characterise the dispersion efficiency of additives, with a detection threshold of 2.3 wt% above which very local heterogeneity can be determined by this technique. CRI provided microstructure information for the entire binary structure formed by the fibre network. The fibre dispersion and orientation depend on their location in the matrix, and the specific surface of the fibres increases with the fibre content as aggregates start to develop. The technique also highlighted a possible core-skin effect in the injected composite

Oct 15, 2016

Ferulic acid-based renewable esters and amides-containing epoxy thermosets from wheat bran and beetroot pulp: Chemo-enzymatic synthesis and thermo-mechanical properties characterization

Ferulic acid-based renewable esters and amides-containing epoxy thermosets from wheat bran and beetroot pulp: Chemo-enzymatic synthesis and thermo-mechanical properties characterization

In this study, ferulic acid – a natural phenolic acid present in bagasse, wheat and rice brans, and beetroot pulp – was used as renewable starting material to prepare new biobased epoxy precursors. This biobased building block was first esterified then reduced to provide ethyl dihydroferulate which was then trans-esterified/amidified with biobased diols, triol and diamines. Immobilized Candida antarctica (aka CAL-B or Novozyme 435®) was used to perform the solvent-free-transesterification/amidation under mild conditions. The phenolic architectures synthesized were then glycidylated using a TEBAC-mediated procedure to afford four biobased epoxy precursors – with various linker structures between the ferulic units – which were then cured with conventionnal and biobased diamine curing agents. The thermal and thermomechanical properties of the thermosets prepared were assessed by TGA, DSC and DMA to highlight the influence of the linker configuration (aliphatic vs cycloaliphatic), that of the epoxy functionality (di vs tri), and that of the nature of the function used for coupling ferulic units (ester vs amide) on the thermosets properties. Analyses of these thermosets revealed glass transition temperatures ranging from 32 to 85 °C and high thermal stabilities around 300 °C. The mechanical behavior of the biobased thermosets proved equivalent to that of the DGEBA-IPDA reference sytem at low temperatures (up to 40–100 °C depending on the epoxy precursor and diamine).

Sep 16, 2016

Ferulic Acid-Based Bis/Trisphenols as Renewable Antioxidants for Polypropylene and Poly(butylene succinate)

Ferulic Acid-Based Bis/Trisphenols as Renewable Antioxidants for Polypropylene and Poly(butylene succinate)

Green chem. principles recommend the use of renewable feedstocks and biocatalysis to decrease environmental impact of chems. manufg.  In this scope, three ferulic acid-​based bisphenols and one trisphenol were synthesized using enzymic catalysis.  Their antioxidant activity at polymer processing and service temp. was investigated in polypropylene (PP) and polybutylene succinate (PBS)​, and benchmarked against the com. antioxidant Irganox 1010.

The anal. of the oxygen induction time of the polymer degrdn. at high temps. showed that Irganox 1010 was more efficient to protect PP than the ferulic acid-​based bis​/trisphenols, whereas, in the case of PBS, the biobased antioxidants, and in particular tris-​O-​dihydroferuloyl glycerol (GTF)​, were more efficient. FT-​IR anal. of neat and formulated PP with different antioxidants stored for 2 years at room temp. showed no degrdn. Aging studies of PBS at room temp. in dry atm. showed that all antioxidants had an equal stabilizing effect on the mol. wt. avs. of the polymer. In conclusion, ferulic acid-​based antioxidants can be efficient primary antioxidants for the thermo-​oxidative stabilization of polymers.

Sep 09, 2016

Optimization of the Laccase-Catalyzed Synthesis of Syringaresinol and Study of its Thermal and Antiradical Activities

Optimization of the Laccase-Catalyzed Synthesis of Syringaresinol and Study of its Thermal and Antiradical Activities

We report herein an optimized biocatalytic oxidative process for the synthesis of syringaresinol from sinapyl alc. at a multigram scale (93​% yield) in very high yield.  Syringaresinol thereby obtained is of sufficient chem. purity and exhibits good thermal and antiradical activities to be used without further purifn. in many applications related to polymer synthesis as an alternative to bisphenol A.  Different mechanistic pathways were discussed to better understand the impact of reaction conditions on the type of linkage formed during the oxidative process.  Antiradical activity (DPPH anal.) and thermal properties of syringaresinol are also discussed.

Jun 29, 2016

Chemo-Enzymatic Synthesis of Chiral Epoxides Ethyl and Methyl (S)-3-(Oxiran-2-yl)propanoates from Renewable Levoglucosenone: An Access to Enantiopure (S)-Dairy Lactone

Chemo-Enzymatic Synthesis of Chiral Epoxides Ethyl and Methyl (S)-3-(Oxiran-2-yl)propanoates from Renewable Levoglucosenone: An Access to Enantiopure (S)-Dairy Lactone

Herein, starting from levoglucosenone (LGO)​, a biobased chiral compd. was obtained through the flash pyrolysis of acidified cellulose, a safer and more sustainable chemo-​enzymic synthetic pathway involving lipase-​mediated Baeyer-​Villiger oxidn., palladium-​catalyzed hydrogenation, tosylation and treatment with sodium ethoxide​/methoxide as key steps was proposed.  This route afforded Et and Me (S)​-​3-​(oxiran-​2-​yl)​propanoates in 57​% overall yield, resp.  To demonstrate the potentiality of this new synthetic pathway from LGO, the synthesis of high value-​added (S)​-​dairy lactone was undertaken from these epoxides and provided the target in 37​% overall yield from LGO.

Jun 02, 2016

Structure property relationships of biobased n-alkyl bisferulate epoxy resins

Structure property relationships of biobased n-alkyl bisferulate epoxy resins

In this work, a series of bio-​based chem. recyclable epoxy resins were synthesized from n-​alkyl bisferulate esters that do not activate human estrogen receptor alpha (ERα)​.  Viscosities of corresponding glycidyl ether n-​alkyl bisferulate resins, detd. by steady shear rheol., range from 12-​9.4 Pa s.  Activation energies of flow range from 83-​96 kJ mol-​1 and are similar to the diglycidyl ether bisphenol A (DGEBA)​.  Thermomech. properties of diglycidyl ether n-​alkyl bisferulate resins cured with isophorone diamine were governed by the length of α,​ω-​diols that link glycidyl ether ferulate units.  That is, the glassy phase modulus and alpha transition temps. range from 3400-​2400 MPa (at 25 °C) and 40-​53 °C (peak of E'')​, resp.  Furthermore, the onset of thermal degrdn. (Td5​%) varied from 331-​300 °C.

Chem. recycling of cured epoxy resins was performed by static immersion in 10 wt.​/wt. sodium hydroxide aq. solns. at 60 °C. Times required for complete conversion of cured resins to water-​sol. degrdn. products was also α,​ω-​diol length dependent and varied from 5 to 65 h. Thus, diglycidyl ether of n-​alkyl bisferulate resins provides a viable biobased alternative to BPA epoxy resins as well as the option of chem. degradability and recovery of fillers in composite applications.

Apr 27, 2016

ADMET polymerization of biobased monomers deriving from syringaresinol

ADMET polymerization of biobased monomers deriving from syringaresinol

Renewable α,​Ω-​dienes have been prepd. from syringaresinol, a naturally occurring bisphenol deriving from sinapyl alc., and further studied as monomers in ADMET polymns.  Polymn. was optimized according to catalyst loading and reaction conditions (in mass vs. in solvent)​, and led to polymers with mol. wt. up to 14.1 kDa.  Thermal analyses of these new polymers showed excellent thermal stabilities (257-​360°) and tunable Tg (18-​70°) depending on the structure of the starting α,​Ω-​diene monomer.

Apr 19, 2016

Lipase-Catalyzed Baeyer-Villiger Oxidation of Cellulose-Derived Levoglucosenone into (S)-g-Hydroxymethyl-Butenolide: Optimization by Response Surface Methodology

Lipase-Catalyzed Baeyer-Villiger Oxidation of Cellulose-Derived Levoglucosenone into (S)-g-Hydroxymethyl-Butenolide: Optimization by Response Surface Methodology

Cellulose-​derived levoglucosenone (LGO) has been efficiently converted into pure (S)​-​γ-​hydroxymethyl-​α,​β-​butenolide (HBO)​, a chem. platform suited for the synthesis of drugs, flavors and antiviral agents.  This process involves two-​steps: a lipase-​catalyzed Baeyer-​Villiger oxidn. of LGO followed by an acid hydrolysis of the reaction mixt. to provide pure HBO.  Response surface methodol. (RSM)​, based on central composite face-​centered (CCF) design, was employed to evaluate the factors effecting the enzyme-​catalyzed reaction: pka of solid buffer (7.2-​9.6)​, LGO concn. (0.5-​1 M) and enzyme loading (55-​285 PLU.mmol-​1)​.

Enzyme loading and pka of solid buffer were found to be important factors to the reaction efficiency (as measured by the conversion of LGO) while only the later had significant effects on the enzyme recyclability (as measured by the enzyme residual activity)​. LGO concn. influences both responses by its interaction with the enzyme loading and pka of solid buffer. The optimal conditions which allow to convert at least 80​% of LGO in 2 h at 40°C and reuse the enzyme for a subsequent cycle were found to be: solid buffer pka = 7.5, [LGO] = 0.50 M and 113 PLU.mmol-​1 for the lipase. A good agreement between exptl. and predicted values was obtained and the model validity confirmed (p < 0.05)​. Alternative optimal conditions were explored using Monte Carlo simulations for risk anal., being estd. the exptl. region where the LGO conversion higher than 80​% is fulfilled at a specific risk of failure.

Feb 15, 2016

Chemo-enzymatic preparation and characterization of renewable oligomers with bisguaiacol moieties: promising sustainable antiradical/antioxidant additives in situ product recovery

Chemo-enzymatic preparation and characterization of renewable oligomers with bisguaiacol moieties: promising sustainable antiradical/antioxidant additives in  situ product recovery

The synthesis, structural characterization and properties of new bio-​based oligomers with bisguaiacol-​type moieties esterified by diverse aliph. linkers are described.  These oligomers, produced by oxidative oligomerization of renewable dihydroferulic acid-​based bisphenols with com. available Trametes versicolor laccase, are proposed as promising sustainable antiradical​/antioxidant additives for polymers.  This environmentally friendly biocatalyzed process is performed under very mild conditions in open vessels and aq. soln. at room temp.

Modifications of the reaction conditions (use of an org. co-​solvent up to 80​% vol.​/vol. and increase of the reaction temp. up to 60 °C) revealed that the polymn. degree of the oligomers may be controlled by adjusting the nature and the ratio of the co-​solvent, the reaction time and the reaction temp. Thermal analyses (TGA and DSC) demonstrated that these phenolic oligomers exhibit high thermal stability and that their Td 5​% and Tg can be easily tailored by playing with both the structure of the bisphenol and the d.p. Similarly, these phenolic oligomers exhibit tunable potent antiradical​/antioxidant activity as shown by DPPH analyses. These aliph.-​arom. oligomers with bisguaiacol-​type moieties are thus promising as easily accessible, eco-​friendly antiradical​/antioxidant additives for the stabilization of polymers in packaging and other applications.

Jan 07, 2016

Reactive extraction of bio-based 3-hydroxypropionic acid assisted by hollow-fiber membrane contactor using TOA and Aliquat 336 in n-decanol

Reactive extraction of bio-based
3-hydroxypropionic acid assisted by hollow-fiber membrane contactor using TOA and Aliquat 336 in n-decanol

Reactive liq.-​liq. extn. is a promising technique for the direct recovery of carboxylic acids from bioconversion media.  This work focused on the optimization of 3-​hydroxypropionic acid (3-​HP) reactive extn. assisted by hollow-​fiber membrane contactor (HFMC)​, using tri-​n-​octylamine (TOA) and Aliquat 336 as extractants in n-​decanol, and on its practical application for the recovery of 3-​HP obtained from glycerol bioconversion by Lactobacillus reuteri.  The results underlined the influence of the initial pH and 3-​HP concn. of the aq. medium and the impact of extractant phase compn. on the extn. performances.

The highest distribution coeff. of 3-​HP (KD = 13.0) was obsd. at pH = 3 with 10​% vol.​/vol. TOA mixed with 10​% vol.​/vol. Aliquat 336 in n-​decanol. This study showed that the acid concn. and the ratio of amines used between TOA and Aliquat 336 in n-​decanol did not have a great impact on the KD during 3-​HP reactive extn., whereas it had an influence on the extn. kinetics. Moreover, 3-​HP reactive extn. assisted by HFMC from real bioconversion broth with glycerol as the substrate was shown to be feasible, with the same order of magnitude of extn. kinetics but with a lower KD compared with reactive extn. using model broth. 3-​HP was predominantly extd. from the bioconversion broth, confirming the high selectivity of the extn. process studied and the high potential of this approach applied to the biotechnol. prodn. of 3-​HP.

Jan 06, 2016

Monitoring of free phenol content in lignosulfonates by ClO2 titration and UV difference spectroscopy

Monitoring of free phenol content in lignosulfonates by ClO2 titration and UV difference spectroscopy

Lignosulfonates (LS) are water-soluble polyphenolic macromolecules derived from lignins and common industrial additives in plasticizers and dispersants. A key feature for a more efficient utilization of modified LS is the monitoring of their free phenol (OHphen) content during various reactions as these phenols govern a large part of their chemical reactivity. Against this background, the UV difference spectroscopy (Δεi method) and ClO2 titration have been revisited. Synthetic LS model compounds with a SO3H group on their benzylic position and H, G, and S aromatic rings were synthesized and used to assess the suitability of both the ClO2 titration and the Δεi method on LS. The methodology combining the two analytical methods was then used to determine the molar extinction coefficient of a given LS allowing the calibration of the Δεi method for a convenient and rapid monitoring of OHphen in the course of LS reactions involving the OHphen groups.

Dec 11, 2015

Ultrafast Photoprotecting Sunscreens in Natural Plants

Ultrafast Photoprotecting Sunscreens in Natural Plants

We explore the ultrafast photoprotective properties of a series of sinapic acid derivs. in a range of solvents, utilizing femtosecond transient electronic absorption spectroscopy.  We find that a primary relaxation mechanism displayed by the plant sunscreen sinapoyl malate and other related mol. species may be understood as a multistep process involving internal conversion of the initially photoexcited 11ππ* state along a trans-​cis photoisomerization coordinate, leading to the repopulation of the original trans ground-​state isomer or the formation of a stable cis isomer.

Nov 16, 2015

Structure−Activity Relationships and Structural Design Optimization of a Series of p‑Hydroxycinnamic Acids-Based Bis- and Trisphenols as Novel Sustainable Antiradical/Antioxidant Additives

Structure−Activity Relationships and Structural Design Optimization of a Series of p‑Hydroxycinnamic Acids-Based Bis- and Trisphenols as Novel Sustainable Antiradical/Antioxidant Additives

Chemo-​enzymic synthesis and screening of a library of renewable satd. and unsatd. bis- and trisphenols deriving from p-​hydroxycinnamic acids (i.e., p-​coumaric acid, ferulic acid, and sinapic acid) and biobased diols​/triol (i.e., isosorbide, 1,​4-​butanediol, glycerol) showed that these compds. were potent antioxidants​/antiradicals.  To optimize their antiradical activities, we assessed the structure-​activity relationships (SAR) of these phenolics focusing on the internal diol​/triol linker, the degree of methoxylation on the arom. rings, and the C=C double bond of the α,​β-​unsatd. esters.  We found that methoxylation degree and the unsatn. were crit. for antiradical activity while the nature of the diol had a small impact.  Indeed, SAR revealed that, for satd. compds., the higher the methoxylation degree, the higher the antiradical activity; on the other hand, unexpectedly, the presence of the unsatn. had a neg. impact on the activity.

The antiradical activities of these bis- and trisphenols were then compared to that of Irganox 1010, a widely used antioxidant additive in polypropylene. The optimized compds., i.e. those deriving from sinapic acid and with satd. esters, proved as effective while being 100​% biobased and obtained through a more sustainable synthetic pathway. Thermal analyses (TGA) demonstrated that these bis- and trisphenols exhibit high thermal stability and that their Td5​% can be easily tailored by playing with the structure of the bisphenol core. p-​Hydroxycinnamic acids-​based bis- and trisphenols are thus promising easily accessible, eco-​friendly, and biocompatible antiradical additives for a sustainable approach to the stabilization of polymers in packaging and other applications.

Oct 23, 2015

3-Hydroxypropionaldehyde (3-HPA) quantification by HPLC using a synthetic acrolein-free 3-hydroxypropionaldehyde system as analytical standard

3-Hydroxypropionaldehyde (3-HPA) quantification by HPLC using a synthetic acrolein-free 3-hydroxypropionaldehyde system as analytical standard

HPLC-​based quantification of 3-​HPA using a synthetic acrolein-​free 3-​HPA std. obtained from com. available 1,​2,​4-​butanetriol through a straightforward and easy synthetic process has advantages over previous colorimetric methods of easier and safer implementation, and greater specificity.  This HPLC method is very simple to implement in a lab, does not need any extra handling of the sample to be analyzed, and is suitable even in the presence of other aldehydes and 3-​HPA derivs., provided that the latter do not have similar retention times.

Sep 07, 2015

Reactive extraction of 3-hydroxypropionic acid from model aqueous solutions and real bioconversion media. Comparison with its isomer 2-hydroxypropionic (lactic) acid

Reactive extraction of 3-hydroxypropionic acid from model aqueous solutions and real bioconversion media. Comparison with its isomer 2-hydroxypropionic (lactic) acid

Bioconversion is a promising route to produce bio-​based building blocks such as 3-​hydroxypropionic acid (3-​HP)​.  Reactive extn. can be used for 3-​HP recovery, and ultimately integrated to the bioconversion process.  To the best of our knowledge, there is no published exptl. data about the reactive extn. of 3-​HP.  This work aimed to study the extn. of 3-​HP using tri-​n-​octylamine and Aliquat 336 as extractants in n-​decanol.  Comparison was also made with its positional isomer, lactic acid.  Finally, the extn. of 3-​HP from model and real bioconversion broths was examd.

Bioconversion is a promising route to produce bio-​based building blocks such as 3-​hydroxypropionic acid (3-​HP)​.  Reactive extn. can be used for 3-​HP recovery, and ultimately integrated to the bioconversion process.  To the best of our knowledge, there is no published exptl. data about the reactive extn. of 3-​HP.  This work aimed to study the extn. of 3-​HP using tri-​n-​octylamine and Aliquat 336 as extractants in n-​decanol.  Comparison was also made with its positional isomer, lactic acid.  Finally, the extn. of 3-​HP from model and real bioconversion broths was examd.  The use of mixed extractants showed high performances over a wide range of exptl. conditions, highlighting a synergistic effect.  A possible extn. mechanism considers the formation of a ternary complex between TOA, Aliquat 336 and the carboxylic acid.  When 3-​HP was extd. from a real bioconversion broth, some cell-​originating compds. were suspected to adsorb to the aq.-​org. interface.  This effect, added to the possible competition between 3-​HP and compds. that can react with the extractants, led to limitations in the yield (Y​%) and selectivity (α3HP) of the extn.  For example, Y​% and α3HP were resp. 89​% and 35.9 for the model bioconversion broth and decreased to 62​% and 15.7 for the real broth at pH = 3.2.  Effective exptl. conditions for the reactive extn. of 3-​HP were pointed out for the first time.  Further work will be undertaken with a view to better elucidating the mechanisms involved in real conditions of an integrated extractive bioconversion system.

Aug 29, 2015

Diversity of Lactobacillus reuteri Strains in Converting Glycerol into 3-Hydroxypropionic Acid

Diversity of Lactobacillus reuteri Strains in Converting Glycerol into 3-Hydroxypropionic Acid

The present study aims at comparing the performances of three Lactobacillus reuteri strains (DSM 20016, DSM 17938, and ATCC 53608) in producing 3-​hydroxypropionic acid (3-​HP) from glycerol and at exploring inhibition phenomena during this bioconversion.  Differences were highlighted between the three strains in terms of 3-​HP prodn. yield, kinetics of substrate consumption, and metabolite prodn.  With a maximal productivity in non-​optimal conditions (free pH) around 2 g.L-​1.h-​1 of 3-​HP and 4 g.L-​1.h-​1 of 3-​hydroxypropionaldehyde (3-​HPA) depending on the strain, this study confirmed the potential of L. reuteri for the biotechnol. prodn. of 3-​HP.  Moreover, the molar ratios of 3-​HP to 1,​3-​propanediol (1,​3-​PDO) obtained for the three strains (comprised between 1.25 and 1.65) showed systematically a higher 3-​HP prodn.

The DSM 17938 strain appeared to be the most promising strain. The impact of glycerol bioconversion on the bacteria's physiol. state (a decrease of ∼40​% in DSM 17938 cells showing an enzymic activity after 3 h) and survival (total loss of cultivability after 2 or 3 h depending on the strains) was revealed and discussed. The effect of each metabolite on L. reuteri DSM 17938 was further studied, displaying a drastic inhibition caused by 3-​HPA, while 3-​HP induced lower impact and only at acidic pH.

Aug 13, 2015

Relationships between the use of Embden Meyerhof pathway (EMP) or Phosphoketolase pathway (PKP) and lactate production capabilities of diverse Lactobacillus reuteri strains

Relationships between the use of Embden Meyerhof pathway (EMP) or Phosphoketolase pathway (PKP) and lactate production capabilities of diverse Lactobacillus reuteri strains

The aims of this study is to compare the growth and glucose metab. of three Lactobacillus reuteri strains (i.e. DSM 20016, DSM 17938, and ATCC 53608) which are lactic acid bacteria of interest used for diverse applications such as probiotics implying the prodn. of biomass, or for the prodn. of valuable chems. (3-​hydroxypropionaldehyde, 3-​hydroxypropionic acid, 1,​3-​propanediol)​.  However, the physiol. diversity inside the species, even for basic metabs., like its capacity of acidification or glucose metab., has not been studied yet.  In the present work, the growth and metab. of three strains representative of the species diversity have been studied in batch mode.  The strains were compared through characterization of growth kinetics and evaluation of acidification kinetics, substrate consumption and product formation.

The results showed significant differences between the three strains which may be explained, at least in part, by variations in the distribution of carbon source between two glycolytic pathways during the bacterial growth: the phosphoketolase or heterolactic pathway (PKP) and the Embden-​Meyerhof pathway (EMP)​. It was also shown that, in the context of obtaining a large amt. of biomass, DSM 20016 and DSM 17938 strains were the most effective in terms of growth kinetics. The DSM 17938 strain, which shows the more significant metabolic shift from EMP to PKP when the pH decreases, is more effective for lactate prodn.

Nov 29, 2014

Renewable polymers derived from ferulic acid and biobased diols via ADMET

Renewable polymers derived from ferulic acid and biobased diols via ADMET

Renewable α,​ω-​diene monomers have been prepd. from ferulic acid, biosourced diols (isosorbide and butanediol) and bromo-​alkenes using a chemo-​enzymic synthetic pathway then studied as monomers in ADMET polymn.  All monomers and polymers have been thoroughly characterized using NMR, GPC, DSC and TGA.  ADMET polymn. was optimized with regard to catalyst loading (Hoveyda-​Grubbs II)​, reaction medium (in mass vs. in solvent)​, and temp., which led to polymers with mol. wt. up to 25 kDa.  Thermal anal. of these new poly(ester-​alkenamer)​s showed excellent thermal stabilities (283-​370 °C) and tunable Tg depending on the nature of the biobased diol and the chain length of the alkene in the α,​ω-​diene monomer.

Nov 22, 2014

Renewable alternating aliphatic-aromatic poly(ester-urethane)s prepared from ferulic acid and bio-based diols

Renewable alternating aliphatic-aromatic poly(ester-urethane)s prepared from ferulic acid and bio-based diols

A new class of eight partially renewable alternating aliph.-​arom. poly(ester-​urethane)​s (PEUs) is obtained through the polyaddn. of four renewable bisphenols derived from ferulic acid and bio-​based diols on two com. available diisocyanates.  The structures and mol. wts. of these PEUs are characterized by 1H and 13sC NMR, Fourier transform IR spectroscopy (FT-​IR)​, and size exclusion chromatog. (SEC)​.  The PEUS are further studied by thermogravimetric anal. (TGA) and differential scanning calorimetry (DSC)​.  All these thermoplastic PEUs are transparent and rigid at room temp., with Mn ranging from 4 to 10 kDa, and relatively narrow dispersities (1.7-​3.5)​, prove to be stable up to more than 180 °C (Td 5​%)​, with Tg varying from 28 to 128 °C depending on their structure.

Oct 08, 2014

Plant Sunscreens in the UV-B: Ultraviolet Spectroscopy of Jet-Cooled Sinapoyl Malate, Sinapic Acid, and Sinapate Ester Derivatives

Plant Sunscreens in the UV-B: Ultraviolet Spectroscopy of Jet-Cooled Sinapoyl Malate, Sinapic Acid, and Sinapate Ester Derivatives

UV spectroscopy of sinapoyl malate, an essential UV-​B screening agent in plants, was carried out in the cold, isolated environment of a supersonic expansion to explore its intrinsic UV spectral properties in detail.  Despite these conditions, sinapoyl malate displays anomalous spectral broadening extending well over 1000 cm-​1 in the UV-​B region, presenting the tantalizing prospect that nature's selection of UV-​B sunscreen is based in part on the inherent quantum mech. features of its excited states.  Jet-​cooling provides an ideal setting in which to explore this topic, where complications from intermol. interactions are eliminated.  In order to better understand the structural causes of this behavior, the UV spectroscopy of a series of sinapate esters was undertaken and compared with ab initio calcns., starting with the simplest sinapate chromophore sinapic acid, and building up the ester side chain to sinapoyl malate.

This "deconstruction" approach provided insight into the active mechanism intrinsic to sinapoyl malate, which is tentatively attributed to mixing of the bright V (1ππ*) state with an adiabatically lower 1nπ* state which, according to calcns., shows unique charge-​transfer characteristics brought on by the electron-​rich malate side chain. All members of the series absorb strongly in the UV-​B region, but significant differences emerge in the appearance of the spectrum among the series, with derivs. most closely assocd. with sinapoyl malate showing characteristic broadening even under jet-​cooled conditions. The long vibronic progressions, conformational distribution, and large oscillator strength of the V (ππ*) transition in sinapates makes them ideal candidates for their role as UV-​B screening agents in plants.

Sep 05, 2014

Chemo-enzymatic synthesis of key intermediates (S)-γ-hydroxymethyl-α,β-butenolide and (S)-γ-hydroxymethyl-γ-butyrolactone via lipase-mediated Baeyer–Villiger oxidation of levoglucosenone

Chemo-enzymatic synthesis of key intermediates (S)-γ-hydroxymethyl-α,β-butenolide and (S)-γ-hydroxymethyl-γ-butyrolactone via lipase-mediated Baeyer–Villiger oxidation of levoglucosenone

Levoglucosenone (LGO)​, a valuable chiral platform chem. that can be efficiently produced from catalytic fast pyrolysis of cellulose, has been efficiently converted into optically pure (S)​-​γ-​hydroxymethyl-​α,​β-​butenolide (HBO) using a two-​step sequence involving a lipase-​mediated Baeyer-​Villiger oxidn. and an acid hydrolysis.  In the same fashion, (S)​-​γ-​hydroxymethyl-​γ-​butyrolactone (2H-​HBO) was successfully obtained through a three-​step sequence (Baeyer-​Villiger, palladium-​catalyzed hydrogenation and acid hydrolysis)​.  The use of solid buffers in the lipase-​mediated Baeyer-​Villiger oxidn. has proved beneficial in two ways: not only the reaction time and the enzymic load were both reduced four-​fold (from 8 to 2 h and 464 to 113 U mmol-​1) to reach conversions ≥83​%, but solid buffers also prevented lipase from denaturation, thus preserving its enzymic activity and allowing its use for further oxidn. cycles.

Jan 29, 2014

Renewable Alternating Aliphatic–Aromatic Copolyesters Derived from Biobased Ferulic Acid, Diols, and Diacids: Sustainable Polymers with Tunable Thermal Properties derived from ferulic acid

Renewable Alternating Aliphatic–Aromatic Copolyesters Derived from Biobased Ferulic Acid, Diols, and Diacids: Sustainable Polymers with Tunable Thermal Properties
derived from ferulic acid

Renewable alternating aliph.-​arom. copolyesters are obtained through the polycondensation of biobased diacyl chlorides and bisphenols derived from ferulic acid and biosourced diols.  The Tg of these thermoplastics can be tailored to closely match those of petroleum-​based poly(ethylene terephthalate) (PET) and also give access to applications requiring polyesters with lower glass-​transition temps.

Apr 22, 2013

Chemo-enzymatic preparation of new bio-based bis and trisphenols: new versatile building blocks for polymer chemistry

Chemo-enzymatic preparation of new bio-based bis and trisphenols: new versatile building blocks for polymer chemistry

Immobilized Candida antartica lipase B (aka CAL-​B) was used to perform solvent-​free and in solvent transesterifications of a deriv. from ferulic acid (1)​, Et dihydroferulate (2)​, with various bio-​based polyols (isosorbide, 1,​3-​propanediol, 1,​4-​butanediol and glycerol)​.  The use of 1.5 M eq of Et dihydroferulate (2) per alc. functionality and CAL-​B (10​% by wt. relative to the total wt. of polyol and 2) led to the corresponding poly-​ferulates (3-​6) in very good yields and high purity.  These poly-​ferulates were then efficiently transformed through one-​step processes into the corresponding acrylates (7-​10) and allyl ethers (11-​14) to demonstrate their potential use as biorenewable macromonomers in a wide range of polymn. systems.