To maximize their potential for intended applications, technical fibers such as flax (Linum usitatissimum L.) need to be processed via mechanical or physicochemical methods. Among these, enzymatic and ultrasonic degumming treatments make it possible to modify the material while adhering to green chemistry principles. However, the combination of these treatments to achieve new characteristics has not yet been well investigated in plant fibers, although it is applied to many other lignocellulosic materials. In this study, the first objective was to determine favorable degumming conditions for the enzymatic hydrolysis and ultrasonic irradiation of technical flax fiber. To this end, the impacts of different pectinase cocktails and low-frequency ultrasound conditions on the composition of technical flax fibers were investigated via a screening design. On the basis of these results, the effects of various treatments and their combination on the diameter, surface finish, and thermal and mechanical properties of well-characterized fibers were studied. Notably, the use of a pectate lyase-based cocktail (BioPrep 3000 L) was shown to refine technical fibers by 16-34%, while improving their traction modulus up to 42-76%. Moreover, the use of ultrasound downstream of pectate lyase treatment enhanced the thermal properties and cleaned the fiber surfaces, while reducing the breaking properties up to 20-34%. These impacts have been shown to depend on the raw fiber state. The use of these treatments and their combination is therefore subject to compromises depending on the properties targeted and would require further investigation to achieve optimization.

Atomic Force Microscopy in PeakForce Quantitative NanoMechanics mode (AFM PeakForce QNM) under controlled relative humidity (RH) was applied to continuously monitor the indentation modulus (IM) of Norway spruce (Picea abies) earlywood (EW) and latewood (LW) tracheid cell walls over three absorption/desorption (S/D) cycles. The IM of the different cell wall layers were close between early- and latewoods indicating small differences between their chemical compositions. AFM nanoInfraRed measurements (AFM NanoIR) indicate variations in lignin and cellulose with an increase of lignin and a decrease of cellulose from the S2 to the S1 and finally to the CC (cell corner). Earlywood and latewood cell walls display the same hygronanomechanical behavior during S/D cycle, i.e., the IM values decrease during absorption up to 85

AFM PeakForce QNM under controlled relative humidity (RH) was applied to continuously monitor the indentation modulus (IM) of Norway spruce ( Picea abies ) earlywood (EW) and latewood (LW) tracheid cell walls over three sorption/desorption (S/D) cycles. The IM of the different cell wall layers were close between early- and latewoods indicating small differences between their chemical compositions. AFM IR indicate a gradient of lignin and cellulose across the cell wall with an increase of lignin and a decrease of cellulose from the S2 to the S1 and finally to the CC. Earlywood and latewood cell walls display the same hygro–nanomechanical behavior during S/D cycle, i.e., the IM decrease with during sorption up to 85% and re–increase during desorption. Gaussian fits of the IM distribution were narrower for late wood than early wood and vary with the type of layer and with the relative humidity. The responses of the indentation moduli to RH of the cell wall layers in early- and latewood were fitted according to a three-parameter logistic function. Significant differences are observed for the S2 in both EW and LW indicating a higher slope in the response of indentation moduli to RH between 15 and 50% RH in desorption as compared to sorption. For both desorption and sorption, the comparison between EW vs LW reveals differences in CC and S1, with a higher slope in moduli response to RH in LW between 15 and 50% RH and the opposite between 50 to 85% RH.

Natural fibres are well known for their high efficiency in evaporation and humidification applications, making them a promising solution for cooling processes during heat waves. Mimicking the evapotranspiration mechanisms of trees is essential for designing optimal fibre wicks in canopy-like devices. Such devices are designed by their capillary rising height and water storage capacity. This study examines the water retention properties and capillary rise height of various yarns: retention tests for surface properties and tomographies for topographical aspects are combined to explain observed water rising height in samples. Tomographic analyses document pore sizes, fibre diameters, and water distribution within the wicks. Water retention properties among the samples range from less than 10% to over 20% of dry mass, reflecting significant wettability differences. However, the ultimate height of water ascension primarily depends on the structural yarn properties. Repeated tomographic scans during the rise reveal that water initially ascends in fibre dense regions. The competition between capillary and tensile forces causes displacements, redistributing fibre densities. In plant fibres, swelling amplifies these displacements and propagates them along the wick axis. Water envelops individual fibres or bundles, penetrating into the lumens. The size of wet lumens increases due to internal capillary pressure, which is influenced by the convexity of the internal walls. This pressure drives a creeping progression of the water front along the fibre axis. The study finds that a high number strings with intermediate porosities, which accommodate swelling, enhances the capillary rise height. However, further research is needed to fully understand the role of lumens. While they provide additional water storage capacity and facilitate capillary action through small diameters, they may also reduce the flow rate of water ascent.

Understanding the anaerobic deconstruction of recalcitrant lignocellulose remains challenging. Combining substrate composition and transcriptomic analyses, we shortlisted Ruminiclostridium cellulolyticum enzymes that modify lignocelullose and distinguished two members of the large SGNH hydrolase superfamily potentially enhancing lignocellulosic biomass degradation by acting on decorations of lignin and hemicelluloses but also on cross-links implicating lignin. Using genetic modifications, bioinformatics and biochemistry, we show they promote the plant cell wall ester-linked hydroxycinnamic acid derivatives release, a role never described for these proteins mainly synthesized by the restricted group of cellulolytic and cellulosome-producing bacteria. In addition to the recent observation of fungal limited lignin alterations in oxygen absence, this discovery is to the best of our knowledge, the first evidence of such anaerobic bacterial process that provides a better comprehension of the biogeochemical Earth's carbon cycle. Furthermore, a better knowledge of the anaerobic plant biomass degradation could help to design non-fossil resources based biotechnological applications, a cornerstone of bioeconomy development.

Lignin, produced from papermaking and biorefinery industrial processes, is an interesting green substitute for petroleum-based derivative products with multiple functional properties, including bioplasticizing, bioadhesive, UV resistance and antioxidant properties. Although lignin is a major wood component (20-25 wt%) available in large quantities, it is seldom used industrially because of its difficult handling in the manufacture of high-value products. Controlling the lignin structural morphology in native and composite materials remains challenging because of the wide variety of chemical functional groups influencing its spatial organization and final network physicochemical properties. In thermoplastics applications, improving the interfacial interactions between the lignin charge and polymer matrix is essential. This work reports a combination of experimental approaches to investigate the chemical and adhesive properties of lignin at the molecular level, both in preparation of atomic force microscopy probes and in measurement at a nanometric scale through single-molecule force spectroscopy (SMFS), nano-infrared spectroscopy and imaging. The application of an original Langmuir-Blodgett (LB) deposition procedure produced homogeneous ultrathin coatings with controlled thicknesses in comparison with classical chemical deposition routes. Both procedures were verified for two synthetic lignins, guaiacyl and mixed guaiacyl-syringyl dehydrogenation polymers, before being applied to pine lignin as a proof-of-concept for the development of green lignin-based (nano)composites. Functionalizing the tip via the LB approach increased the adhesion force measurement resolution and provided new insights into the molecular affinity of lignin for other materials at the nanoscale, which prefers xylan polymers, such as those in native plant cell walls, and apolar/polar polymer matrices, such as those in composite materials, albeit to a lesser extent.

Lignins, one of the main components of plant cell wall, and by-products of certain industries (paper and wood industries,…) are a renewable source of aromatic molecules. They can be degraded and transformed by microbial and enzymatic processes known to be respectful of the environment. Biological valorization of lignins remains challenging as biocatalysts are not sufficiently effective and efficient. Moreover, the chemical complexity and heterogeneity of lignins are a barrier to their use. Understanding the microbial behaviour on lignins by fingerprinting their efficient transformation could lead to the development of effective biological routes to valorise these aromatic polymers. Ligninolytic bacteria present some interesting features in term of ligninolytic enzymes productions, utilization of aromatic compounds via various intracellular pathways and the productions of molecules of interest from aromatic molecules. In this work, multiple approaches (growth studies, ligninolytic activities production, lignin modifications and phenolic compounds fingerprints) were used to understand the behaviour of two ligninolytic bacteria Pandoraea norimbergensis and Comamonas composti, in presence of lignins with different structures and origins. Results showed dissimilar growths profiles, lignin modifications, consumption and production of phenolic monomers and oligomers according to the bacteria and the lignin used. To achieve efficient transformation of lignins, suitable combination of biocatalysts and lignins is required and the microorganisms used must be selected on the basis of their metabolic capacity, and the structure and composition of lignin.

Eucalyptus globulus stumps are a by-product from the coppice pulp plantation after three generations. In this study a stump was fractionated in three discs (60 cm between them), and their constituent tissues—heartwood, sapwood and bark—were subjected to further chemical characterization by summative analysis, evaluation of the phytochemical profile and antioxidants activities, plus GC/MS and analytical pyrolysis aiming at their valorization. Wood density was similar between tissues and disc level: values ranging from 0.652 to 0.705 g/cm3 (Disc 1) and 0.605 g/cm3 (Disc 5). Bark had high ash (3.5

Polyethylene glycol (PEG) consolidation treatment is a widely used conservation strategy for wooden culture relics. However, the consolidation mechanism of PEG is still open to interpretation. PEG-cellulose, the representative component of wood cell wall, interactions are governed by various coupled multi-scale mechanisms which require nano-scale investigation. In this study, a hybrid molecular dynamics and grand canonical Monte Carlo (MD/GCMC) simulation combined with rule of mixture (RoM) analyses are employed to reveal the underlying mechanisms of PEG-induced consolidation. We found that PEG200 reduces moisture adsorption and swelling at museological conditions, confirming its consolidation effect. At high PEG content, a crossover behavior is identified at humid conditions (RH > 80) where excessive sorption and swelling are observed surpassing the untreated sample. The molecular modeling results are found to be consistent with experimental observations. Furthermore, the structural and mechanical properties of the hydrated samples are assessed by examining the porosity distribution, mechanical properties, and hydrogen bonding network. Results indicate mechanical softening induced by PEG treatment. A modified mixture model is proposed based on molecular modeling results that incorporate sorption and swelling coupling, porosity filling and mechanical softening behaviors. Two key mechanisms are identified explaining the consolidation effect of PEG: first, the PEG fills the porosities of amorphous structure thus diminishing sorption sites; second, the polymer structure prohibits PEG from further swelling thus constraining water sorption. The model and theoretical framework can serve as a guide for the design of novel consolidant materials by identifying the key molecular features of an ideal consolidant.

Characterizing the hygroscopic behavior of macromolecular assemblies is crucial for understanding biological processes as well as to develop tailor-made polysaccharides-based products. In this work, assemblies consisting of nanocelluloses (CNC or CNF) and/or glucomannan in different ratio were studied at different water activity levels, using a multi-analytical approach that combined Dynamic Vapor Sorption (DVS), Time-Domain Nuclear Magnetic Resonance (TD-NMR) and solid-state NMR (ss-NMR). The water retention capacity of the films, as a function of their composition, showed that an enrichment in konjac glucomannan in association with cellulose increased the water absorption capacity but decreased the water retention capacity. In addition, the combination of CNC and glucomannan appears to reduce the water absorption capacity of each polymer. Correlating the findings from the various methods allowed us to propose the use of TD-NMR data for predicting the water retention capacity. These results, summarized in a schematic representation, offer new insights into the organization of water molecules in polysaccharide assemblies in various humidity conditions.

The industrial process of extracting flax fibers from a plant ( Linum usitatissimum L.), which involves a combination of retting and scutching, could lead to matter heterogeneity within individual roll bales. Although many studies have investigated the variability of flax fiber compositions and properties as functions of various factors throughout the value chain, no researchers have focused on long-fiber bale heterogeneity and its impact on quality. In this work, five batches were empirically identified based on visual and textural criteria, and were subsequently characterized. The study of their differences and similarities using a combination of physicochemical methods allowed them to be classified into several groups, depending on the criteria measured and the structural scale. Thus, variations in surface composition were related to the presence of external tissue residues and microbial biomass but were not related to the measured polysaccharide composition. Additionally, the technical fibers displayed different mechanical and hygroscopic properties, which could be distributed within 2-4 groups, independent of color and surface composition criteria. This study is a first step in determining fiber heterogeneity, which constitutes a global quality assessment for the further application of flax fibers.

Major challenge in biorefineries is the use of all lignocellulosic components, particularly lignins. In this study, Thermobacillus xylanilyliticus grew on kraft lignin, steam-exploded and native wheat straws produced different sets of phenoloxidases and xylanases, according to the substrate. After growth, limited lignin structural modifications, mainly accompanied by a decrease in phenolic acids was observed by Nuclear Magnetic Resonance spectroscopy. The depletion of p-coumaric acid, vanillin and p-hydroxybenzaldehyde combined to vanillin production in the culture media indicated that the bacterium can transform some phenolic compounds. Proteomic approaches allowed the identification of 29 to 33 different hemicellulases according to the substrates. Twenty oxidoreductases were differentially expressed between kraft lignin and steam-exploded wheat straw. These oxidoreductases may be involved in lignin and aromatic compound utilization and detoxification. This study highlights the potential value of Thermobacillus xylanilyticus and its enzymes in the simultaneous valorization of hemicellulose and phenolic compounds from lignocelluloses.

Lignins, abundant aromatic biopolymers and one of the major components of lignocellulosic biomass, remain the most underutilized renewable bioresources of aromatics and hydrocarbons on the Earth. Numerous physical and chemical processes have been developed for lignin valorization; however, they generally suffer from environmentally unfriendly, harsh conditions and lack reaction specificity. On the other hand, milder methods involving biocatalysts exist but are impeded by many limitations, such as cofactor regeneration, deleterious enzyme-lignin interactions, and low stability. In this work, we attempt to eliminate the constrains encountered in enzyme-based lignin valorization processes through the development of a novel electrochemically assisted bioprocess. This "all-in-one" biocathode incorporates a hybrid electrocatalytic interface combining a hydrogen peroxide-generating passive air-breathing gas diffusion electrode with an immobilized hydrogen peroxide-consuming lignin peroxidase on a single surface and catalyzing the depolymerization of lignins. The ligninolytic potential of this bioelectrochemical device is demonstrated using both lignin models (veratryl alcohol and veratrylglycerol beta-guaiacyl ether) and a technical lignin at room temperature in aqueous media with the reaction efficiency of 14.9% per hour.

The data provided here relate to the research paper “Assessing the complementarity of TD-NMR, solid-state NMR and Dynamic Vapor Sorption in the characterization of polysaccharide-water interactions”. The original data from TD-NMR, ss-NMR and DVS is provided in .dps, topspin and .xls formats respectively, allowing other authors to repeat our processing protocols using different parameters. We also include results obtained by varying the signal treatments. The analysis of these multimodal data have highlighted a variation in polysaccharide-water interactions depending on the type of assembly. These datasets are very useful for discriminating between water bound to polysaccharides and water absorbed or adsorbed into polysaccharide network, a key element in understanding interactions in these assemblies and an essential approach for developing tailor-made polysaccharides-based products.

The production of bio-based composites with enhanced characteristics constitutes a strategic action to minimize the use of fossil fuel resources. The mechanical performances of these materials are related to the specific properties of their components, as well as to the quality of the interface between the matrix and the fibers. In a previous research study, it was shown that the polarity of the matrix played a key role in the mechanisms of fiber breakage during processing, as well as on the final properties of the composite. However, some key questions remained unanswered, and new investigations were necessary to improve the knowledge of the interactions between a lignocellulosic material and a polar matrix. In this work, for the first time, atomic force microscopy based on force spectroscopy measurements was carried out using functionalized tips to characterize the intermolecular interactions at the single molecule level, taking place between poly(butylene succinate) and four different plant fibers. The efficiency of the tip functionalization was checked out by scanning electron microscopy and energy-dispersive X-ray spectroscopy, whereas the fibers chemistry was characterized by Fourier-transform infrared spectroscopy. Larger interactions at the nanoscale level were found between the matrix and hypolignified fibers compared to lignified ones, as in control experiments on single lignocellulosic polymer films. These results could significantly aid in the design of the most appropriate composite composition depending on its final use.

Here, we report work on developing an enzymatic process to improve the functionalities of industrial lignin. A kraft lignin sample prepared from marine pine was treated with the high-redox-potential laccase from the basidiomycete fungus Pycnoporus cinnabarinus at three different concentrations and pH conditions, and with and without the chemical mediator 1-hydroxybenzotriazole (HBT). Laccase activity was tested in the presence and absence of kraft lignin. The optimum pH of PciLac was initially 4.0 in the presence and absence of lignin, but at incubation times over 6 h, higher activities were found at pH 4.5 in the presence of lignin. Structural changes in lignin were investigated by Fourier-transform infrared spectroscopy (FTIR) with differential scanning calorimetry (DSC), and solvent-extractable fractions were analyzed using high-performance size-exclusion chromatography (HPSEC) and gas chromatography–mass spectrometry (GC–MS). The FTIR spectral data were analyzed with two successive multivariate series using principal component analysis (PCA) and ANOVA statistical analysis to identify the best conditions for the largest range of chemical modifications. DSC combined with modulated DSC (MDSC) revealed that the greatest effect on glass transition temperature (Tg) was obtained at 130 U g cm−1 and pH 4.5, with the laccase alone or combined with HBT. HPSEC data suggested that the laccase treatments led to concomitant phenomena of oligomerization and depolymerization, and GC–MS revealed that the reactivity of the extractable phenolic monomers depended on the conditions tested. This study demonstrates that P. cinnabarinus laccase can be used to modify marine pine kraft lignin, and that the set of analytical methods implemented here provides a valuable tool for screening enzymatic treatment conditions.

Dew retting, the selective biodegradation of industrial hemp (Cannabis sativa L.) stems after harvest, is a key field process for plant fiber use. The stage of maturity of the crop and the weather conditions during the subsequent dew retting process differ with hemp harvest time, which depends on the hemp valorization scenario. In this work, the aim was to investigate and rank the important factors that drive hemp retting, such as hemp harvest date, weather during retting, soil type under hemp mulch, and their interactions under agricultural field conditions. To this end, an experimental field trial was set up in the northeastern area of France (Champagne region), with two hemp harvest scenarios and two types of soil common to the agricultural area. Physicochemical hemp characteristics and climatic conditions were dynamically monitored during the retting periods. Dynamics of stem characteristics determined at the biomass level (dry matter loss) and the outer tissue level (surface analysis, chemical and thermal analysis) showed that the kinetics of retting followed similar patterns regardless of soil type for both harvest date scenarios. The kinetics were strongly and linearly related to air temperature, expressed as the number of normalized days at 15 degrees C, and to cumulative radiation during retting periods. The cumulative amounts of rain and dew explained the kinetics less than temperature and radiation, regardless of the retting scenario considered. The strong relationship observed between colorimetry and infrared spectroscopic data for characterizing the retting progress for both harvest scenarios paves the way for the development of tools to monitor changes in hemp stem quality.

One of the biggest challenges for a more widespread utilization of plant fibers is to better understand the different molecular factors underlying the variability in fineness and mechanical properties of both elementary and scutched fibers. Accordingly, we analyzed genome-wide transcription profiling from bast fiber bearing tissues of seven different flax varieties (4 spring, 2 winter fiber varieties and 1 winter linseed) and identified 1041 differentially expressed genes between varieties, of which 97 were related to cell wall metabolism. KEGG analysis highlighted a number of different enriched pathways. Subsequent statistical analysis using Partial Least-Squares Discriminant Analysis showed that 73% of the total variance was explained by the first 3 X-variates corresponding to 56 differentially expressed genes. Calculation of Pearson correlations identified 5 genes showing a strong correlation between expression and morphometric data. Two-dimensional gel proteomic analysis on the two varieties showing the most discriminant and significant differences in morphometrics revealed 1490 protein spots of which 108 showed significant differential abundance. Mass spectrometry analysis successfully identified 46 proteins representing 32 non-redundant proteins. Statistical clusterization based on the expression level of genes corresponding to the 32 proteins showed clear discrimination into three separate clusters, reflecting the variety type (spring-/winter-fiber/oil). Four of the 32 proteins were also highly correlated with morphometric features. Examination of predicted functions for the 9 (5 + 4) identified genes highlighted lipid metabolism and senescence process. Calculation of Pearson correlation coefficients between expression data and retted fiber mechanical measurements (strength and maximum force) identified 3 significantly correlated genes. The genes were predicted to be connected to cell wall dynamics, either directly (Expansin-like protein), or indirectly (NAD(P)-binding Rossmann-fold superfamily protein). Taken together, our results have allowed the identification of molecular actors potentially associated with the determination of both in-planta fiber morphometrics, as well as ex-planta fiber mechanical properties, both of which are key parameters for elementary fiber and scutched fiber quality in flax.

BACKGROUND:Lignocellulosic biomass is a complex network of polysaccharides and lignin that requires a pretreatment step to overcome recalcitrance and optimize valorisation into biobased products. Pretreatment of biomass induces chemical and morphological changes. Quantification of these changes is critical to understand biomass recalcitrance and to predict lignocellulose reactivity. In this study, we propose an automated method for the quantification of chemical and morphological parameters through fluorescence macroscopy, which was applied on wood samples (spruce, beechwood) pretreated with steam explosion.RESULTS:Results in fluorescence macroscopy highlighted the impact of steam explosion on spruce and beechwood: fluorescence intensity of samples was highly altered, especially for the most severe conditions. Morphological changes were also revealed: shrinkage of cells and deformation of cell walls manifested as the loss of rectangularity or circular shape, for tracheids in spruce and vessels in beechwood respectively. Quantification of fluorescence intensity of cell walls and quantification of morphological parameters related to cell lumens were carried out accurately by applying the automated method onto the macroscopic images. The results showed that lumens area and circularity could be considered as complementary markers of cell deformation, and that fluorescence intensity of the cell walls could be related to morphological changes and to the conditions of pretreatment.CONCLUSIONS:The developed procedure allows simultaneous and effective quantification of morphological parameters and fluorescence intensity of the cell walls. This approach can be applied to fluorescence macroscopy as well as other imaging techniques and provides encouraging results towards the understanding of biomass architecture.