Search

Lignosulfonates are bio-based surfactants and specialty chemicals, which are generated by breaking the near-infinite lignin network during sulfite pulping of wood. Due to their amphiphilic nature, lignosulfonates are used in manifold applications such as plasticizer, dispersant, and stabilizer formulations. Function and performance are determined by their behavior in aqueous solution and at surfaces and interfaces, which is in turn imposed by the chemical make-up. This review hence summarizes the efforts made into delineating the physicochemical properties of lignosulfonates, while also relating to their composition and structure. Lignosulfonates are randomly branched polyelectrolytes with abundant sulfonate and carboxylic acid groups to ensure water-solubility. In aqueous solution, their conformation, colloidal state, and adsorption at surfaces or interfaces can be affected by a range of parameters, such as pH, concentration of other electrolytes, temperature, and the presence of organic solvents. These parameters may also affect the adsorption behavior, which reportedly follows Langmuir isotherm and pseudo second-order kinetics. The relative hydrophobicity, as determined by hydrophobic interaction chromatography, is an indicator that can help to relate composition and behavior of lignosulfonates. More hydrophobic materials have been found to exhibit a lower charge density. This may improve dispersion stabilization, but it can also be disadvantageous if an electrokinetic charge needs to be introduced at solid surfaces or if precipitation due to salting out is an issue. In addition, the monolignol composition, molecular weight distribution, and chemical modification may affect the physicochemical behavior of lignosulfonates. In conclusion, the properties of lignosulfonates can be tailored by controlling aspects such as the production parameters, fractionation, and by subsequent modification. Recent developments have spawned a magnitude of products and technologies, which is also reflected in the wide variety of possible application areas.

Lignin is the second-most abundant biopolymer in nature and remains a severely underutilized waste product of agriculture and paper production. Sulfur is the most underutilized byproduct of petroleum and natural gas processing industries. On their own, both sulfur and lignin exhibit very poor mechanical properties. In the current work, a strategy for preparing more durable composites of sulfur and lignin, LSx, is described. Composites LSx were prepared by reaction of allyl lignin with elemental sulfur, whereby some of the sulfur forms polysulfide crosslinks with lignin to yield a three-dimensional network. Even relatively small quantities (

The study focuses on delignification of Kraft pulp using carbamide peroxide as bleaching agent. The Kappa number reduction of bleached pulp is favored at low consistency of pulp and higher reaction temperature. The optimal Kappa reduction was achieved at temperature of 68 °C, 0.8 g of carbamide peroxide per 100 ml of solution and 2% consistency in the range of variables studied. Fourier transform infrared spectral analysis done on bleached pulp to determine bond stretches and bending vibrations. X ray diffraction spectral data observation provided that the crystallinity index increased from 81.7% before bleaching to 85% after bleaching which indicates the removal of amorphous species in sample. FT-RAMAN spectral analysis concludes the possible conformational changes pre and post bleaching. The absence of some native lignin bands post bleaching indicates lignin removal. Scanning electron microscope images of bleached pulp samples were observed with less amounts of fibrillar type lignin network on surface of pulp fibers when compared to unbleached samples. The activation energy and rate constants were determined for delignification of pulp using carbamide peroxide process. Sequential treatment of Kraft pulp with carbamide peroxide and sodium percarbonate were also evaluated.

Alternative renewable energy must emerge to sustainably meet the energy demands of the present and future. Current alternatives to fossil fuels are electricity from solar, wind and tidal energies and biofuels. Biofuels, especially bioethanol could be produced from lignocellulosic feedstock via pre-treatment and fermentation. The cellulose I content of most lignocellulosic feedstock is significant, yet its highly crystalline amphiphilic structure interlinked with the lignin network makes it difficult to process for bioethanol production. Processing lignocellulosic biomass via a range of physico-chemical, mechanical and biological pre-treatment methods have been well established, however a relatively new area on the use of cellulose II (a polymorph of native cellulose obtained via mercerisation or regeneration) for the production of bioethanol is still in its early stages. Hence, this review discusses in detail the advantages of using cellulose II over cellulose I as feedstock for bioethanol production. Furthermore, current green and sustainable methods for cellulose II production and the advantages and disadvantages of each method are discussed. In addition, examples from literature reporting higher fermentable sugar and bioethanol yields using cellulose II as feedstock are reviewed, thereby highlighting its importance in the field of bioethanol production. The conclusion from this review suggests that, in all the cases studied, fermentable sugar and/or bioethanol production was found to be higher when cellulose II was used as feedstock instead of native cellulose/lignocellulosic biomass. This higher yield could be attributed to the modified structural and lattice arrangement of cellulose II, its porous volume and degree of polymerisation. Postprint

Sweet sorghum bagasse (SSB) generated in large quantities could be hydrolyzed to sugar and then fermented to green fuels. The hydrolysis of SSB polysaccharides interlocked in recalcitrant lignin network is the major problem. Pretreatment of SSB in SSF by using Coriolus versicolor with CuSO4-syringic acid supplements for effects on production of ligninocellulolytic enzymes, lignin degradation and selectivity values (SV) were studied. C. versicolor was selected based on high ligninolytic and low cellulolytic abilily. Individually, CuSO4 increased the activities of laccase (4.9 folds) and PPO (1.9 folds); syringic acid increased LiP (13 folds), AAO (2.8 folds) and laccase (5.6 folds) resulting in increased lignin degradation and SVs. Combined syringic acid (4.4 μmol g−1 SSB) and CuSO4 (4.4 μmol g−1 SSB) increased the activities of laccase, LiP, MnP, PPO and AAO by 11.2, 17.6, 2.8, 2.4 and 2.3 folds respectively due to synergistic effect, resulting in maximum lignin degradation 35.9 ± 1.3% (w w−1) (1.86 fold) and highest SV 3.07 (4.7 fold). Enzymatic hydrolysis of pretreated SSB yielded higher (∼2.2 times) fermentable sugar. Pretreated SSB was characterized by XRD, SEM, FTIR and TGA/DTG analysis to confirm results. It is possible to improve fungal pretreatment of agricultural waste by combination of supplements.

This study tests the hypothesis that thermal modification of wood influences the effectivity of air plasma treatment. Micro-veneers of European beech, Scots pine and Norway spruce were thermally modified at two different temperatures and subsequently plasma-treated for 1 and 3 s. The veneer surfaces were characterized in terms of morphology, wetting behaviour and surface chemistry. No severe changes in the veneer surfaces due to plasma treatment were observed by scanning electron microscopy. Plasma treatment increased surface free energy and wettability by water and urea-formaldehyde adhesive; it was more effective on thermally modified wood than on unmodified wood. X-ray photoelectron spectroscopy revealed a similar distribution of oxygen-containing functional groups on the wood surface after plasma treatment of thermally modified and unmodified beech wood. It is suggested that enhanced wettability through plasma treatment is due to the generation of carboxyl groups within the lignin network, which contribute to the polar part of the surface free energy. The high effectiveness of plasma treatment on thermally modified wood might thus be explained by its high relative proportion of lignin.

This study focused on providing a chemical understanding of the effect of pyrolysis temperature on the pyrolytic depolymerization of lignin polymers in biomass. The lignin network consists of various linkages with phenyl propane units and can be destroyed by the cleavage of various linkages, such as β- O -4, α- O -4, β-β, and β-5. Among of the linkage, the most abundant linkages are β- O -4, which account for more than 40% of the total linkages in softwood lignin and up to 60% in hardwood lignin. For investigating the cleavage of β-aryl ether linkages leading to depolymerization of the lignin polymer, β- O -4 lignin dimer models, guaiacylglycerol-β-guaiacyl ether, guaiacylglycerol-β-coniferyl ether, and p -hydroxyphenylglycerol-β-coumaryl ether were subjected to analytical pyrolysis at various temperatures. Abundant pyrolysis products were identified, and the effect of temperature on the product composition was analyzed. Several cleavage pathways of β-aryl ether linkages have been proposed on the basis of the compositions and structures of the pyrolysis products. The manner of β-aryl ether cleavage is highly susceptible to the pyrolysis temperature, with most secondary products being produced in high yield upon high-temperature pyrolysis.

The bovine rumen hosts a diverse microbiota, which is highly specialized in the degradation of lignocellulose. Ruminal bacteria, in particular, are well equipped to deconstruct plant cell wall polysaccharides. Nevertheless, their potential role in the breakdown of the lignin network has never been investigated. In this study, we used functional metagenomics to identify bacterial redox enzymes acting on polyaromatic compounds. A new methodology was developed to explore the potential of uncultured microbes to degrade lignin derivatives, namely kraft lignin and lignosulfonate. From a fosmid library covering 0.7 Gb of metagenomic DNA, three hit clones were identified, producing enzymes able to oxidize a wide variety of polyaromatic compounds without the need for the addition of copper, manganese, or mediators. These promiscuous redox enzymes could thus be of potential interest both in plant biomass refining and dye remediation. The enzymes were derived from uncultured Clostridia, and belong to complex gene clusters involving proteins of different functional types, including hemicellulases, which likely work in synergy to produce substrate degradation.

Bio-energy production from lignocelluloses biomass has gained a lot of interest in recent years. Miscanthus sp. are high lignocelluloses biomass yielding with relatively high carbohydrate content cultivable on different soils and under climatic conditions. However, the lignocellulosic nature means that cellulose and hemicellulose are cover by lignin network that might limit hydrolysis. In this study, physical pretreatments (size reduction), physiochemical (steam expulsion) and chemical pre-treatments (mild acid and alkaline) were investigated in a view to improve the anaerobic biodegradability of Miscanthus lutarioriparius for biogas production. Prior to the pretreatment and methane potential test, the compositional analyses of M. lutarioriparius was performed in order unveil the carbohydrate (cellulose and hemicelluloses), protein and lignin contents. From these analyses, the maximum theoretical methane potential was estimated. All pretreatments led to solubilisation of organic matter as was evidenced by increase dissolve COD and ammonium nitrogen. There was a positive correlation between dissolved COD and methane yields meanwhile a negative correlation was observed for reducing sugar and methane yields. The achieved methane yields ranged from 121 to 238 ml CH4/g VS. Steam explosion, 0.3 M NaOH treatment and 0.5 mm size reduction led to the highest increases in methane yields, which was in the order of 57% with regard to the untreated samples. These improvements resulted in 71% of theoretical methane yield of M. lutarioriparius. Alkaline pretreatment in particular also improve the rate of methane production as was evidenced by the fact that as high 15% of the final methane yield that was achieve on the first day as compared to only 3% for the untreated sample. Indeed, the time to reach 90% of the ultimate methane yield was reduced by 13 days following 0.3 M NaOH treatment. M. lutarioriparius may therefore represent an interesting candidate as a lignocellulosic feedstock for biogas production after suitable pretreatment. (C) 2015 Elsevier Ltd. All rights reserved. (Less)

Alum-treated archaeological woods from the Oseberg collection, excavated and treated in the early 1900s demonstrate an extreme deterioration, only discovered in the past decade. This research was aimed at understanding the characteristics of the naturally aged material through chemical analyses of both organic and inorganic components, in order to provide information for the preservation/conservation of these precious objects. Analytical pyrolysis-gas chromatography/mass spectrometry with in situ silylation using hexamethyldisilazane (Py(HMDS)-GC/MS) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) were used to investigate a set of samples of alum-treated archaeological wood and untreated archaeological wood. Sound woods of the same species were also analysed in order to compare the results. Results from Py(HMDS)-GC/MS analyses of alum-treated woods from Oseberg showed an extreme depletion of carbohydrates and a highly deteriorated lignin network. The majority of the lignin had undergone oxidation reactions, illustrated by high relative amounts of acidic pyrolysis products. In particular, p-hydroxy-benzoic acid was detected for the first time as a degradation product of archaeological wood. Results from ICP-AES showed variable concentrations of aluminium and potassium from the alum treatment, as well as iron, copper, zinc and calcium. The extent of oxidation observed by Py(HMDS)-GC/MS appeared to correlate with relative amounts of iron and calcium in the samples, which may suggest that degradation promoted by iron compounds is inhibited in the presence of calcium compounds. The results obtained for a sample of archaeological wood treated with alum salts five years ago showed that chemical deterioration of lignin had already begun, mainly involving depolymerisation reactions, though only a slight increase in oxidation was evident. In addition to increased insight into potential deterioration reactions, occurring in a complex material such as alum-treated archaeological wood, it was possible to relate the degree of chemical degradation of the Oseberg woods to their visual condition (observed with the naked eye).

Lignin is an aromatic polymer that makes a network by intertwining between cellulose fibers in plant. As the lignin network retards access to carbohydrates, it is regarded as a nuisance during biomass processing. When wood is processed into paper pulp or bioethanol, lignin is produced as a by-product and utilized as fuel or a soil amendment. Recently, there has been much interest in the aromatic structure of lignin in relation to the utilization of lignocellulose and the search for petroleum substitutes. Sulfur-free pulping methods, such as soda-anthraquinone cooking, provide more opportunity for using lignin than the alternative kraft process. Our aim was to expand the availability of soda lignin from Japanese cedar, the most planted tree in Japan, by fungal degradation. We performed degradation assays to identify suitable fungi for the efficient breakdown of soda lignin from cedar. Fourteen fungi from both white-rot and leaf-litter fungi were identified using the RBBR and Sundman and Nase assays. By nuclear magnetic resonance analysis we obtained water- and/or methanol-soluble degradation products from four fungi, and the patterns indicate specific degradation mechanisms for each fungi. These results suggest that the screened fungi have more than one mechanism for degrading soda lignin from Japanese cedar.

Low molecular mass acetylated organosolv lignin from wheat straw and from depolymerised low sulphur organosolv wood lignin have been shown to markedly improve both the water resistance and the mechanical performance of welded dowel wood joints. The acetylated oligomers distribution and extent of acetylation of the two lignins were determined by Matrix assisted laser desorption ionization-time-of-flight mass spectrometry. Extensive acetylation was confirmed by CP-MAS 13C NMR spectrometry. Force–displacement measurements on welded dowel joints to which acetylated wood lignins were added showed a ductile behaviour. This is due to the interpenetration of the elastic acetylated lignin network into the more rigid composite network of the welded interphase.

International audience; Production of energy from lignocellulosic biomass or residues is receiving ever-increasing interest. Among the different processes, dark fermentation for producing biohydrogen and anaerobic digestion for producing biomethane present considerable advantages. However, they are limited by the accessibility of holocelluloses that are embedded in the lignin network. The authors propose a review of works on the conversion of biomass into biohydrogen and biomethane with the comprehensive description of (a) biomass composition and features that may impact on its anaerobic conversion and (b) the impact of different kinds of pretreatment on these features and on the performance of biohydrogen and methane production.

The release kinetics of esterified p-coumaric acid (PCA) and ferulic acid (FA) from rice straw under a mild alkaline condition were investigated to collect fundamental data for the design of a recovery process. The results showed that the straw size, NaOH concentration, and temperature were the key parameters governing release kinetics. The analysis demonstrated that FA is released considerably faster than PCA. The close relationship between lignin and the PCA dissolution indicates a reciprocal and/or simultaneous release. Moreover, PCA is broadly distributed in the lignin network but tends to be located more densely in the lignin fraction which is not easily solubilized by alkaline treatment. In contrast, the release of FA is strongly affected by removal of lignin fraction which is easily solubilized. These results suggest that the release kinetics are controlled by the accessibility of NaOH to their ester sites in the lignin/hemicellulose network, and by their localization.

Two analytical procedures based on gas chromatography and mass spectrometry were used to study the compositions of a wild population and a selected clone (Torviscosa) of giant reed ( Arundo donax L.), one of the most promising biomass both in terms of energy and fine chemicals production. Gas chromatography/mass spectrometry (GC/MS) was used to characterize and quantitatively determine the monosaccharide composition. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), using hexamethyldisilazane (HMDS) as a derivatising agent, was used to characterize the lignocellulosic polymers. Analytical pyrolysis was also used to study the composition of residues left after the catalytic hydrolysis used to convert cellulose to levulinic acid and hemicellulose to furfural. GC/MS allowed us to determine the monosaccharide composition and polysaccharide content of the giant reed samples, highlighting that there was no significant difference between the wild population and the selected clone. GC/MS also highlighted that the giant reed leaves have a higher percentage (roughly 60%) of polysaccharide material than the stalks, which contain approximately 50%. Py-GC/MS, following the disappearance of the pyrolysis products of polysaccharides, showed that 150 °C and 190 °C are the best temperatures to obtain the complete catalytic conversion of hemicellulose and cellulose, respectively. Analytical pyrolysis also highlighted that in the course of catalytic hydrothermal conversion a partial depolymerisation of lignin was obtained. In particular, the formation of lignin units containing free phenol groups via the cleavage of the β-aryl ether bonds was demonstrated. The presence of these free phenols in the lignin network suggests the possible exploitation of lignin residues as antioxidant components or in high value biopolymer industries rather than the traditional use as low-value fuel for energy production.

Summary Lithium-sulfur (Li-S) batteries are of considerable interest for high-density energy storage. However, the adoption of Li-S batteries to date has been severely plagued by the polysulfide shuttling effect, whereby polysulfide molecules dissolve into the electrolyte and shuttle across the separator to react with the anode materials, leading to a rapidly fading capacity. Herein, by directly coating a thin layer of reduced graphene oxide (rGO)/sodium lignosulfonate (SL) composite on the standard polypropylene (PP) separator, we produce a rGO@SL/PP separator with abundant negatively charged sulfonic groups in the porous lignin network, which effectively suppress the translocation of the negatively charged polysulfide (PS) ions without compromising the transport of positively charged Li+ ions. Using the rGO@SL/PP separator, we demonstrate a highly robust Li-S battery with a capacity retention of 74% over 1,000 cycles. This study defines an effective strategy to inhibit the PS shuttling effect for highly robust Li-S batteries.

A blend of spruce ( Picea spp.) and fir ( Abies spp.) sawdust was liquefied by an optimized technique in the presence of multifunctional alcohols and p -toluene sulfonic acid monohydrate as a catalyst. The lignin behaviour during wood liquefaction was studied at different reaction times. Samples prepared by the new separation procedure were characterized by quantitative 31 P, 13 C NMR and by size-exclusion chromatography. The final products showed increased molar masses indicating the condensation reactions between the lignin and the multifunctional alcohols. Aliphatic chains were found to be incorporated into the lignin network after liquefaction. The resulting polymer showed an increased content of aliphatic hydroxyl groups with respect to the starting material and a high degree of solubility in multifunctional alcohols.

In order to achieve sustainable conversion of lignocellulosics through the phase-separation process, p-hydroxybenzoic acid (p-HBA) attached to core lignin through ester linkage was used as a reagent for lignin conversion. During the phase-separation treatment with p-HBA, the viscosity of reaction mixture was higher, compared with the phase-separation treatment with p-cresol. By centrifugation of the reaction mixture, the thick interfacial solid materials were formed. The yields of lignophenol, its low molecular weight fraction (separated to the organic layer) and the interfacial solid fraction were about 30%, 30% and 40%, respectively. In case of phase-separation treatment with p-cresol, the yields of lignophenol and its low molecular weight fraction (separated to the organic layer) were about 73% and 27%, respectively. The peak ratio of phenol to guaiacol plus syringol in the pyrogram of lignophenol (p-HBA type) was higher than those of lignophenol (p-cresol type) and Klason lignin. The peak of non-conjugated carbonyl group in the FT-IR spectrum of lignophenol (p-HBA type) was higher than that of the material synthesized without p-HBA. These results indicated that p-HBA was grafted to EFB lignin. The lignophenol (p-HBA type) had higher thermal stability, compared with lignophenols (p-Cresol type). The interfacial solid material between the organic and aqueous layers had higher thermal stability than sulfuric acid lignin. These results suggest the formation of lignin network through p-HBA.

The correlation times, T, of stable pyrroline nitroxyl radicals were determined in solutions of thioglycolic acid lignin from birch pulp dissolved in dioxane, pyridine, or dimethyl sulfoxide-water at 298 and 325 K. It was found that T decreases continously with temperature, but increases with increasing lignin concentration. In pyridine and dimethyl sulfoxide-water, the lignin seems to behave as a nearly compact sphere, whereas in dioxane a more loose structure occurs in accordance with the correlation time data. However, the rigidity of the lignin network is evident in all cases investigated.

Very low surface area (ca. 0.5 m2/g) and a low pore volume (ca. 0.002 cm3/g) have been obtained for oven dried wood, using the nitrogen adsorption technique. The microporous structure of wood flour was partially preserved by the solvent exchange drying (SED) employed in this study, in particular when toluene was used as a final solvent. However, the resulted surface area (ca. 6 m2/g) and a pore volume values (ca. 0.015 cm3/g) indicated that such a structure is in no way representative of a fully swollen cell wall. By using solvent exchange drying (SED), it is possible to preserve the swollen pore structure of holocellulose samples. However, with samples which contain significant amounts of lignin, such as native wood, it is not possible to prevent re-collapse of the pores. This problem arises because as micropore swelling occurs, the surrounding lignin network of the cell wall is stretched. When the molecules occupying the micropores are removed, the lignin returns to its original configuration, re-collapsing the micropores in the process. Chemical modification resulted in significant reduction in surface area and pore volume, possibly a result of pore blocking by the large acyl group.

The use of mediator-based processes for the delignification of wood pulps is of great interest as they promise to be environmentally as well as economically interesting alternatives to the currently dominating chlorine-based processes. Mediator-based processes suffer from the fact that substantial amounts of the mediator molecules are irreversibly lost during the reactions. We have now analyzed in detail the primary and in addition the secondary reactions of the oxime type mediators violuric acid and dimethylvioluric acid with lignin model compounds and softwood pulp in order to find the reasons for the repeatedly reported loss of mediator molecules during enzymatic and electrochemical delignification processes. Using a set of lignin model compounds, representing the various structural subunits in the lignin network, we were able to demonstrate that the loss of mediator is not due to the primary reaction of the mediator radicals with the lignin but occurs in a secondary reaction where the activated lignin subunits react with the mediators in the solution. The primary reaction of the mediator radicals is hydrogen abstraction from phenols and activated aromatic rings which leads to the formation of phenoxyl and phenyl radicals. The secondary reaction is the formation of colored semi-stable covalent adduct molecules from an activated lignin subunit with a mediator molecule in the solution leading to polycyclic N-hydroxy compounds. Only in this secondary reaction mediator molecules are removed from the solution due to covalent attachment to the lignin network. No reaction with the cellulose content in the pulp is observed. The findings reported in this paper point the way to an improved mediator design and appropriately modified processes, where the secondary mediator reactions are suppressed, and removes a major road block towards a technical application of the mediator-based delignification procedures.

We successfully dissolved cedar powder with tetrabutylphosphonium hydroxide ([P4 4 4 4]OH) aqueous solution at 60°C. The dissolution was accelerated by the addition of H2O2. At the initial stage, cellulose was more soluble than hemicellulose and lignin. Both hemicellulose and lignin were gradually dissolved in this solution containing H2O2. Cellulose chains were revealed to be cut into shorter chains in this solution. The lignin network was also found to be partly broken at 60°C. These steps induced components with higher-molecular-weight fractions that cannot be extracted with polar ionic liquids to dissolve. Also, low-molecular-weight fractions such as vanillin and 5-(hydroxymethyl)furfural were found in the resulting solution. Breakage of ether bonds of polysaccharides and lignin and further oxidation were attributed to the active oxygens generated from H2O2. The aqueous mixture reported here is a protocol that can be used to dissolve woody biomass under mild conditions.

金沢大学ナノマテリアル研究所 / 金沢大学理工研究域生命理工学系, Biomass was dissolved in ionic liquids under non-thermal atmospheric pressure plasma irradiation. On plasma irradiation, the amount of dissolved biomass in the ionic liquids increased from 15 to 29mg for bagasse and from 26 to 36mg for Japanese cedar. The high solubility was attributed to the deconstruction of the lignin network by active chemical species generated by the plasma. Selective extraction of cellulose from biomass was observed under plasma irradiation. © CSIRO 2017., This study was also partly supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science. | Japan Society for the Promotion of Science 日本学術振興会

The study of the degradation carried out by microorganisms on plant cell walls poses several problems in the analysis of the degraded solid materials. In this article this analytical problem has been studied by solid-state, high-resolution, carbon-13 cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) and Fourier-transformed infrared (FT-IR) spectroscopy. These two nondestructive techniques proved to be able to give insights into the modifications at a molecular level that the cell wall components undergo during attack by Basidiomycetes fungi. Spruce ( Pinus sylvestris ) and beech wood samples ( Fagus sylvatica ) were exposed for 6 weeks to the activity of brown-rot ( Coniophora puteana ) and white-rot ( Coriolus versicolor ) fungi. Brown-rot fungi appeared preferentially to degrade the polysaccharides, leaving a modified lignin network, whereas white-rot fungi were able to degrade extensively both the polysaccharides and the lignin. A quantitative approach based on integration of CP/MAS NMR spectra showed that spruce lignin was degraded to 77% of its weight by brown-rot, and to 39% by white-rot fungi.

Structural changes of wood and its components have been studied after shear deformation under high pressure (SDHP) at up to 6 GPa. Cellulose amorphization and chain depolymerization was observed. Approximately 30% of microcrystalline cellulose was soluble in water after a 360-degree twist of the Bridgman anvils. The water-insoluble part was re-crystallized into cellulose II lattice. Repeated treatment applied to the nondissolved part of the sample, the so-called cascade experiment, permits the dissolving of about 30% of the residual nondissolved material once again. Extraction with water, followed by 10% sodium hydroxide, allows almost complete dissolving of microcrystalline cellulose (98%). Water-soluble saccharides were studied by HPLC and 13C NMR. It was found that destruction of the wood lignin network needs more severe treatment conditions than cellulose destruction does. Lignin domains in wood act as “grinding stones” during cellulose destruction. Long-living lignin free radicals have been detected with EPR after SDHP. 13C NMR CP/MAS spin diffusion studies showed that SDHP leads to separation of wood components into different biopolymer domains, which turns the system toward thermo-dynamic equilibrium. SDHP does not permit achievement of initial compulsary compatibility of components in native wood. SDHP technique appears as a promising method for wood delignification and carbohydrate saccharification in the solid state without using harmful chemical reagents of solvents, which is important for technological safety and ecology. © 1994 John Wiley & Sons, Inc.

Dilatometry of Japanese cedar wood treated with sodium borate, ammonium bromide and sodium chloride was carried out according to the procedure described previously. The sodium borate-treated wood first underwent shrinkage due to bond formation in hemicelluloses, such as cross-linking and grafting, then elongation due to the chain scission of cellulose, and finally shrinkage due to bond formation in cellulose. The ammonium bromide-treated wood first revealed elongation, secondly shrinkage, then elongation again, and finally shrinkage. These changes are respectively ascribable to the chain scission of cellulose, the cross-linking or grafting of cellulose, the chain scission of cellulose accelerated by the increase in tensile stress from the decrease in cross-sectional area of the specimens, and the cross-linking or grafting of cellulose after active weight loss. The dimensional changes of the sodium chloride-treated wood followed basically the same pattern as that for the ammonium bromide-treated wood, although the first elongation occurred at higher temperatures and progressed through two steps which were attributable to the scissions of linkages in the lignin network and in cellulose, respectively. The activation energies determined for dimensional changes are discussed in relation to the applied tensile loads. Activation energies for weight losses are also presented.

The essential chemical modifications involving the polymeric constituents of wood in friction welding occur in the first 5–6 s slowing down or even stopping afterwards. FT-IR and CP-MAS 13C NMR of the welded area of wood have shown dehydration and an apparent increase in the crystallinity of cellulose. A certain level of hemicelluloses degradation occurs, accompanied by the generation of some furfural. Cellulose degradation is instead very slight. Both analytical techniques show an increase in the proportion of lignin in the welding interphase. A proportion of methoxy groups of lignin is de-etherified to phenolic hydroxy groups. Self-condensation of lignin occurs by internal rearrangement with the formation of Ar–Ar and Ar–CH2–Ar bridges. This progresses throughout the whole process of welding. The formation of C–O–C bridges, although stopping after 6 s welding, at the start of wood carbonisation, also appears to contribute to the increase in cross-linking of the lignin network.

Peroxidases and laccases are key enzymes in the lignin biodegradation process. They oxidize phenolic and non-phenolic lignin model compounds into their phenoxy and cation radicals, respectively. Further non-enzymatic evolution lead then to various C-C and ether bond cleavages. Nevertheless, almost no information on the structural alterations undergone in vitro or in situ by lignin after enzymatic catalysis is available. We report here on the molecular structure of lignin oxidized by various (per)oxidasic systems. The oxidizability of phenolic and non-phenolic structures of the guaiacyl and syringyl type in the lignin network will be discussed as well as the modification of the macromolecular properties of the polymer oxidized in situ or in isolated state.

A CrO3/guajacyl polymeric complex was prepared and characterized. The increased crosslinking of the lignin network in wood afforded by the equivalent CrO3/guajacyl units complexes as well as the insolubility of these complexes are the cause of the enhanced water resistance presented by the CrO3-treated wood. Chromium trioxide was found to be the complexing species. Chromium (VI) was not reduced to chromium (III) during the treatment. A parallel with the lignosulfonates/dichromate gel formation was made.

In order to understand the characteristic solubility of Gramineae ligins in alkali, three lignin fractions were extracted from wheat straw: an alkali-soluble lignin LA, a milled-straw lignin LM and an enzyme lignin LE. Molecular size distributions were compared by size exclusion chromatography on mu-Bondagel, and acidic groups (carboxylic and phenolic groups) were estimated by potentiometric titration. The molecular size distribution of alkali lignin LA was intermediate between those of LM and LE. Solubilisation of wheat straw lignin by alkali treatments may thus result from depolymerisation to molecular weights of the same order as those obtained by ultragrinding. Alkali lignin was found to be significantly richer in acidic groups than LM or LE. It is concluded that Gramineae lignins differ from hardwood and softwood lignins by a relatively higher content of alkali-labile linkages within the lignin network or between lignin and polysaccharides.

The kinetic behavior of a Cr6+/Cu2+ system in its reaction with wood has been elucidated. The same reactions with carbohydrates and lignin of wood for CrVI alone are still present. Approximately 20% of the copper is fixed to the guaiacyl units of lignin in the form of copper chromate; the remaining copper forms complexes with cellulose and mainly with the guaiacyl units of lignin. The CrVI/lignin guaiacyl unit complexes already found for the treatment of wood with CrO3 are still the main CrVI complexes formed. Copper chromate is present as [Cu(H2O)2(guaiacol)]CrO4(guaiacol) complexes, and CuCrO4 bridges between different guaiacyl units of the lignin network appear to be likely. Substantial interference of the Cu2+ ions in the second-zone reactions of CrVI with wood occurs. The amount of CrVI and CrIII fixed onto lignin and cellulose compares well with experimental values. Rate constants, energies of activation, and Arrhenius equations of the various reactions have been obtained. The amount of Cu2+ interference in the reaction has also been calculated.

Spruce wood sawdust has been pretreated with sodium hypochlorite at pH 8 and hydrolyzed into glucose by cellulases of Trichoderma viride at different initial concentrations of substrate and enzyme. The initial rate of hydrolysis was shown to obey a Michaelis type equation and the limiting yield is very high. The kinetics are different for the untreated substrate hydrolyzed under the same conditions; low conversion into glucose is obtained even at very long reaction times. The higher reactivity of the pretreated substrate is explained by a significant increase in the number of accessible anhydroglucose units due to oxidation of the lignin network by sodium hypochlorite. Inhibition of the hydrolysis by glucose and by enzyme adsorption is considered. A simple kinetic scheme is proposed to explain the results. © 1986 American Chemical Society.

A pretreatment of lignocellulosic materials with sodium hypochlorite-hypochlorous acid at controlled pH (between 7 and 9) considerably increases the accessibility of the cellulosic part of the substrate to chemical and biochemical reactants. As a consequence, the yield and rate of the enzymatic hydrolysis to glucose is largely in creased. Wheat straw and spruce sawdust have been investigated. The increase in accessibility is assigned to degradation and (or) de tachment of the lignin network. The loss in cellulose and hemicellulose is not important, lignin being preferentially degraded under carefully controlled pH conditions. When applied to pure cel lulose, the pretreatment decreases the yield of enzymatic hydrolysis; in the absence of lignin, oxidation of the anhydroglucose units is im portant and results in the inhibition of the enzymatic hydrolysis. © 1985 Humana Press Inc.

Beside the phenolic and quinone groups present in lignin which may affect retardation of the polymerization reactions of some vinyl monomers, the lignin network structure, the monomer configuration and the residual carbohydrate attached to lignin were found to play an important role. Die im Lignin vorhandenen Phenol- und Chinongruppen konnen bei einigen Vinylmonomeren eine Retardation der Polymerisationsreaktion bewirken. Es wurde gefunden, das daruberhinaus auch die Netzstruktur des Lignins, die Konfiguration der Monomere und der Kohlenwasserstoffrest am Lignin eine wesentliche Rolle bei der Inhibierung spielen.

SYNOPSIS The effect of various metallic oxides and hydroxides on wood waterproofing was investigated. The waterproofing effect was attributed to the type of complexes formed by the metallic oxide with the guaiacol units of the lignin network of wood. The type of structure of the complex formed, as well as its insolubility, contribute to the wood waterproofing, although to a different extent. Only Cr, Zn, Pb and Sn oxides formed insoluble complexes. Of these only Cr and Zn oxides are able to waterproof wood, although to a different extent. This was attributed to their capacity to further cross-link the lignin network in wood, which renders more difficult water penetration and improves wood dimensional stability. While it is necessary for the complexes formed to be insoluble, their insolubility is not the main contributing factor to wood waterproofing and its dimensional stabilisation.