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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.