Effects of exogenous 24-epibrassinolide and brassinazole on negative gravitropism and tension wood formation in hybrid poplar (Populus deltoids × Populus nigra).

MAIN CONCLUSION: Exogenous 24-epibrassinolide (BL) and brassinazole (BRZ) have regulatory roles in G-fiber cell wall development and secondary xylem cell wall carbohydrate biosynthesis during tension wood formation in hybrid poplar. Brassinosteroids (BRs) play important roles in regulating gravitropism and vasculature development. Here, we report the effect of brassinosteroids on negative gravitropism and G-fiber cell wall development of the stem in woody angiosperms. We applied exogenous 24-epibrassinolide (BL) or its biosynthesis inhibitor brassinazole (BRZ) to slanted hybrid poplar trees (Populus deltoids × Populus nigra) and measured the morphology of gravitropic stems, anatomy and chemistry of secondary cell wall. We furthermore analyzed the expression levels of auxin transport and cellulose biosynthetic genes after 24-epibrassinolide (BL) or brassinazole (BRZ) application. The BL-treated seedlings showed no negative gravitropism bending, whereas application of BRZ dramatically enhanced negative gravitropic bending. BL treatment stimulated secondary xylem fiber elongation and G-fiber formation on the upper side of stems but delayed G-fiber maturation. BRZ inhibited xylem fiber elongation but induced the production of more mature G-fibers on the upper side of stems. Wood chemistry analyses and immunolocalization demonstrated that BL and BRZ treatments increased the cellulose content and modified the deposition of cell wall carbohydrates including arabinose, galactose and rhamnose in the secondary xylem. The expression of cellulose biosynthetic genes, especially those related to cellulose microfibril deposition (PtFLA12 and PtCOBL4) was significantly upregulated in BL- and BRZ-treated TW stems compared with control stems. The significant differences of G-fibers development and negative gravitropism bending between 24-epibrassinolide (BL) and brassinazole (BRZ) application suggest that brassinosteroids are important for secondary xylem development during tension wood formation. Our findings provide potential insights into the mechanism by which BRs regulate G-fiber cell wall development to accomplish negative gravitropism in TW formation.

Ethylene signaling induces gelatinous layers with typical features of tension wood in hybrid aspen.

The phytohormone ethylene impacts secondary stem growth in plants by stimulating cambial activity, xylem development and fiber over vessel formation. We report the effect of ethylene on secondary cell wall formation and the molecular connection between ethylene signaling and wood formation. We applied exogenous ethylene or its precursor 1-aminocyclopropane-1-carboxylic acid (ACC) to wild-type and ethylene-insensitive hybrid aspen trees (Populus tremula × tremuloides) and studied secondary cell wall anatomy, chemistry and ultrastructure. We furthermore analyzed the transcriptome (RNA Seq) after ACC application to wild-type and ethylene-insensitive trees. We demonstrate that ACC and ethylene induce gelatinous layers (G-layers) and alter the fiber cell wall cellulose microfibril angle. G-layers are tertiary wall layers rich in cellulose, typically found in tension wood of aspen trees. A vast majority of transcripts affected by ACC are downstream of ethylene perception and include a large number of transcription factors (TFs). Motif-analyses reveal potential connections between ethylene TFs (Ethylene Response Factors (ERFs), ETHYLENE INSENSITIVE 3/ETHYLENE INSENSITIVE3-LIKE1 (EIN3/EIL1)) and wood formation. G-layer formation upon ethylene application suggests that the increase in ethylene biosynthesis observed during tension wood formation is important for its formation. Ethylene-regulated TFs of the ERF and EIN3/EIL1 type could transmit the ethylene signal.

Structural features affecting the enzymatic digestibility of pine wood pretreated with ionic liquids.

Pretreating lignocellulosic biomass with certain ionic liquids results in structural and chemical changes that make the biomass more digestible by enzymes. In this study, pine wood was pretreated with 1-ethyl-3-methylimidazolium chloride/acetate ([C2 mim]Cl and [C2 mim][OAc]) at different temperatures to investigate the relative importance of substrate features, such as accessible surface area, cellulose crystallinity, and lignin content, on enzymatic digestibility. The ionic liquid pretreatments resulted in glucan conversions ranging from 23% to 84% on saccharification of the substrates, with [C2 mim][OAc] being more effective than [C2 mim]Cl. The pretreatments resulted in no delignification of the wood, some loss of cellulose crystallinity under certain conditions, and varying levels of increased surface area. Enzymatic digestibility closely correlated with accessible surface area and porosity measurements obtained using Simons' staining and thermoporosimetry techniques. Increased accessible surface area was identified as the principal structural feature responsible for the improved enzymatic digestibility.

Flavonoid supplementation affects the expression of genes involved in cell wall formation and lignification metabolism and increases sugar content and saccharification in the fast-growing eucalyptus hybrid E. urophylla x E. grandis.

BACKGROUND: Eucalyptus species are the most widely planted hardwood species in the world and are renowned for their rapid growth and adaptability. In Brazil, one of the most widely grown Eucalyptus cultivars is the fast-growing Eucalyptus urophylla x Eucalyptus grandis hybrid. In a previous study, we described a chemical characterization of these hybrids when subjected to flavonoid supplementation on 2 distinct timetables, and our results revealed marked differences between the wood composition of the treated and untreated trees. RESULTS: In this work, we report the transcriptional responses occurring in these trees that may be related to the observed chemical differences. Gene expression was analysed through mRNA-sequencing, and notably, compared to control trees, the treated trees display differential down-regulation of cell wall formation pathways such as phenylpropanoid metabolism as well as differential expression of genes involved in sucrose, starch and minor CHO metabolism and genes that play a role in several stress and environmental responses. We also performed enzymatic hydrolysis of wood samples from the different treatments, and the results indicated higher sugar contents and glucose yields in the flavonoid-treated plants. CONCLUSIONS: Our results further illustrate the potential use of flavonoids as a nutritional complement for modifying Eucalyptus wood, since, supplementation with flavonoids alters its chemical composition, gene expression and increases saccharification probably as part of a stress response.

Contrasting nitrogen fertilization treatments impact xylem gene expression and secondary cell wall lignification in Eucalyptus.

BACKGROUND: Nitrogen (N) is a main nutrient required for tree growth and biomass accumulation. In this study, we analyzed the effects of contrasting nitrogen fertilization treatments on the phenotypes of fast growing Eucalyptus hybrids (E. urophylla x E. grandis) with a special focus on xylem secondary cell walls and global gene expression patterns. RESULTS: Histological observations of the xylem secondary cell walls further confirmed by chemical analyses showed that lignin was reduced by luxuriant fertilization, whereas a consistent lignin deposition was observed in trees grown in N-limiting conditions. Also, the syringyl/guaiacyl (S/G) ratio was significantly lower in luxuriant nitrogen samples. Deep sequencing RNAseq analyses allowed us to identify a high number of differentially expressed genes (1,469) between contrasting N treatments. This number is dramatically higher than those obtained in similar studies performed in poplar but using microarrays. Remarkably, all the genes involved the general phenylpropanoid metabolism and lignin pathway were found to be down-regulated in response to high N availability. These findings further confirmed by RT-qPCR are in agreement with the reduced amount of lignin in xylem secondary cell walls of these plants. CONCLUSIONS: This work enabled us to identify, at the whole genome level, xylem genes differentially regulated by N availability, some of which are involved in the environmental control of xylogenesis. It further illustrates that N fertilization can be used to alter the quantity and quality of lignocellulosic biomass in Eucalyptus, offering exciting prospects for the pulp and paper industry and for the use of short coppices plantations to produce second generation biofuels.

Severity factor coefficients for subcritical liquid hot water pretreatment of hardwood chips.

Single stage and multi-stage liquid hot water pretreatments of mixed hardwood pinchips were investigated at various severities (log R0 = 3.65-4.81) to assess the efficiencies of the pretreatments with respect to achieving high pentose sugar yields and improved enzymatic digestibility of pretreated cellulose. We investigate the effect of pretreatment parameters that is, temperature, and time, as expressed in the severity factor, on the recovery of sugars and hydrolyzability of pretreated cellulose. We find the severity factor, in its widely used form, is an incomplete measure for evaluating the pretreatment efficiencies and predicting overall sugar yields when pretreatment temperatures above 200°C are used. Corrections to the severity factor and its correlation to the measured pretreatment responses (% xylan solubilization, xylan recovery as fermentable sugars, cellulose enzymatic digestibility) indicate a greater influence of temperature on the pretreatment efficiencies than predicted by the commonly used severity factor. A low temperature, long residence time is preferred for hemicellulose dissolution during the pretreatment since the condition favors oligosaccharide and monomeric sugar formation over sugar degradation. On the contrary, high cellulose hydrolyzability is achieved with a high temperature (>200°C), high severity pretreatment when pretreatment is followed by enzyme hydrolysis. In multi-stage pretreatment, the first low-severity pretreatment is optimized for solubilizing fast-hydrolyzing hemicellulose while minimizing formation of furans. The subsequent pretreatment is carried out at over 200°C to recover the difficult-to-hydrolyze hemicellulose fraction as well as to increase susceptibility of pretreated cellulose to enzymes. High recovery (>92%) of hemicellulose-derived pentose sugars and enhanced enzymatic hydrolysis of pretreated cellulose (where >80% glucose yield results with 20 FPU = 32 mg protein/g glucan or 10-13 mg/g initial hardwood) are achieved by applying a multi-stage pretreatment. This work shows how the severity equation may be used to obtain a single characteristic curve that correlate xylan solubilization and enzymatic cellulose hydrolysis as a function of severity at pretreatment temperatures up to 230°C.

Ultrastructure of the innermost surface of differentiating normal and compression wood tracheids as revealed by field emission scanning electron microscopy.

The ultrastructure of the innermost surface of Cryptomeria japonica differentiating normal wood (NW) and compression wood (CW) was comparatively investigated by field emission electron microscopy (FE-SEM) combined with enzymatic degradation of hemicelluloses. Cellulose microfibril (CMF) bundles were readily observed in NW tracheids in the early stage of secondary cell wall formation, but not in CW tracheids because of the heavy accumulation of amorphous materials composed mainly of galactans and lignin. This result suggests that the ultrastructural deposition of cell wall components in the tracheid cell wall differ between NW and CW from the early stage of secondary cell wall formation. Delignified NW and CW tracheids showed similar structural changes during differentiating stages after xylanase or ß-mannanase treatment, whereas they exhibited clear differences in ultrastructure in mature stages. Although thin CMF bundles were exposed in both delignified mature NW and CW tracheids by xylanase treatment, ultrastructural changes following ß-mannanase treatment were only observed in CW tracheids. CW tracheids also showed different degradation patterns between xylanase and ß-mannanase. CMF bundles showed a smooth surface in delignified mature CW tracheids treated with xylanase, whereas they had an uneven surface in delignified mature CW tracheids treated with ß-mannanase, indicating that the uneven surface of CMF bundles was related to xylans. The present results suggest that ultrastructural deposition and organization of lignin and hemicelluloses in CW tracheids may differ from those of NW tracheids.

The response to daylight or continuous ozone of phenylpropanoid and lignin biosynthesis pathways in poplar differs between leaves and wood.

Ozone induces a stimulation of the phenylpropanoid and lignin biosynthesis pathways in leaves but the response of wood, the main lignin-producing tissue, is not well documented. The purpose of this study was to compare the responses of phenylpropanoid and lignin pathways in leaves and stem wood by a simultaneous analysis of both organs. Young poplars (Populus tremula×alba) were subjected either to daylight ozone (200 nL L(-1) during light period) or continuous ozone (200 nL L(-1) during light and dark periods) in controlled chambers. The trees were tilted so as to limit the formation of tension wood to the upper side of the stem and that of opposite wood to the lower side. Continuous ozone fumigation induced more pronounced effects in leaves than daylight ozone. Tension wood and opposite wood displayed similar responses to ozone. Enzyme activities involved in phenylpropanoid and lignin biosynthesis increased in the leaves of ozone-treated poplars and decreased in the wood. All steps involved in phenylpropanoid and monolignol synthesis in leaves and stem wood, were also altered at the transcript level (except coniferyl aldehyde 5-hydroxylase in leaves) suggesting that the responses were tightly coordinated. The response occurred rapidly in the leaves and much later in the wood. Phenylpropanoid and lignin biosynthesis is probably first involved in a defensive role against ozone in the leaves, which would lead to considerable rerouting of the carbon skeletons. The later response of phenylpropanoid and lignin metabolism in wood seemed to result from readjustment to the reduced carbon supply.

Using FTIR spectroscopy to model alkaline pretreatment and enzymatic saccharification of six lignocellulosic biomasses.

Fourier transform infrared, attenuated total reflectance (FTIR-ATR) spectroscopy, combined with partial least squares (PLS) regression, accurately predicted solubilization of plant cell wall constituents and NaOH consumption through pretreatment, and overall sugar productions from combined pretreatment and enzymatic hydrolysis. PLS regression models were constructed by correlating FTIR spectra of six raw biomasses (two switchgrass cultivars, big bluestem grass, a low-impact, high-diversity mixture of prairie biomasses, mixed hardwood, and corn stover), plus alkali loading in pretreatment, to nine dependent variables: glucose, xylose, lignin, and total solids solubilized in pretreatment; NaOH consumed in pretreatment; and overall glucose and xylose conversions and yields from combined pretreatment and enzymatic hydrolysis. PLS models predicted the dependent variables with the following values of coefficient of determination for cross-validation (Q²): 0.86 for glucose, 0.90 for xylose, 0.79 for lignin, and 0.85 for total solids solubilized in pretreatment; 0.83 for alkali consumption; 0.93 for glucose conversion, 0.94 for xylose conversion, and 0.88 for glucose and xylose yields. The sugar yield models are noteworthy for their ability to predict overall saccharification through combined pretreatment and enzymatic hydrolysis per mass dry untreated solids without a priori knowledge of the composition of solids. All wavenumbers with significant variable-important-for-projection (VIP) scores have been attributed to chemical features of lignocellulose, demonstrating the models were based on real chemical information. These models suggest that PLS regression can be applied to FTIR-ATR spectra of raw biomasses to rapidly predict effects of pretreatment on solids and on subsequent enzymatic hydrolysis.

Discrepancy of lignin dissolution from eucalyptus during formic acid fractionation.

Understanding the structure and properties of lignin has important practical significance for its further applications. In this case, eucalyptus was fractionated with 88% formic acid at 101 °C for different durations, and the removal efficiency as well as the chemical structure of lignin at various stages were comparatively analyzed. The obtained data indicated that with increasing reaction time, lignin was continuously removed and the process could be divided into three stages. The lignin dissolution rate was fast first and then slow, and the molecular weight of the dissolved lignin increased with time. The lignin structure was condensed and the molecular weight increased with prolonged of reaction time. Structural analysis indicated that the ß-O-4' structure was largely destroyed, the G-type lignin dissolved early, and the degradation of the S-type lignin became more intensive with increasing reaction time. This is of great help for reaction control as well as the further processing of lignin byproducts.

Comparison of enzymatic saccharification and lignin structure of masson pine and poplar pretreated by p-Toluenesulfonic acid.

p-Toluenesulfonic acid (p-TsOH) with the hydrotropic and recyclable properties is widely used for rapid remove of lignin from lignocelluloses at low temperature (<100 °C). In this work, both softwood masson pine and hardwood poplar were pretreated with p-TsOH under different conditions and then subjected to enzymatic hydrolysis to compare the effect of p-TsOH pretreatment on their saccharification and lignin structure. Results showed p-TsOH has sensitive selectivity to lignin structure during pretreatment. Around 95% of lignin in poplar can be dissolved at 80 °C within 30 min, while for masson pine, the delignification is only 50%. Following enzymatic hydrolysis with cellulase loading of 20 FPU/g-cellulose for 72 h, the highest sugar yield of pretreated poplar and masson pine is 92.13% and 29.46%, respectively, which indicates that p-TsOH pretreatment alone works well with hardwoods (poplar). Structural analysis of removed lignin implies that p-TsOH mainly results in the cleavage of ß-aryl ether bonds of lignin side chains, and the aromatic structure of lignin keeps intact. p-TsOH pretreatment shows the key advantages of low cost and rapid delignification for highly enzymatic saccharification, and provides a promising and green pathway for the development of low cost and sustainable bio-based products for developing a bio-based economy.

Expression profiling and functional analysis of Populus WRKY23 reveals a regulatory role in defense.

WRKY transcription factors are key regulators that activate and fine-tune stress responses, including defense responses against pathogens. We isolated a poplar (Populus tremulaxPopulus alba) cDNA sequence, PtWRKY23, that encodes the ortholog of Arabidopsis WRKY23 and present the functional analysis of WRKY23, with emphasis on its potential role in resistance to rust infection. To investigate the function of PtWRKY23, we examined PtWRKY23 expression after stress treatments by qRT-PCR and generated PtWRKY23-misexpressing plants. Transgenic plants were assessed for resistance to Melampsora rust and were analyzed using the poplar Affymetrix GeneChip and histological techniques to study the consequences of PtWRKY23 misexpression. PtWRKY23 is rapidly induced by Melampsora infection and elicitor treatments and poplars overexpressing and underexpressing PtWRKY23 were both more susceptible to Melampsora infection than wild type. Transcriptome analysis of PtWRKY23 overexpressors revealed a significant overlap with the Melampsora-infection response. Transcriptome analysis also suggests that PtWRKY23 affects redox homeostasis and cell wall-related metabolism, which was confirmed by analyses that showed that PtWRKY23-misexpressing plants have altered peroxidase activity, apparent H(2)O(2) accumulation and lignin deposition. Our results show that PtWRKY23 affects resistance to Melampsora infection and that this may be caused by deregulation of genes that disrupt redox homeostasis and cell wall metabolism.

Formic acid aided hot water extraction of hemicellulose from European silver birch (Betula pendula) sawdust.

Hemicellulose has been extracted from birch (Betula pendula) sawdust by formic acid aided hot water extraction. The maximum amount of hemicellulose extracted was about 70mol% of the total hemicellulose content at 170°C, measured as the combined yield of xylose and furfural. Lower temperatures (130 and 140°C) favored hemicellulose hydrolysis rather than cellulose hydrolysis, even though the total hemicellulose yield was less than at 170°C. It was found that formic acid greatly increased the hydrolysis of hemicellulose to xylose and furfural at the experimental temperatures. The amount of lignin in the extract remained below the detection limit of the analysis (3g/L) in all cases. Formic acid aided hot water extraction is a promising technique for extracting hemicellulose from woody biomass, while leaving a solid residue with low hemicellulose content, which can be delignified to culminate in the three main isolated lignocellulosic fractions: cellulose, hemicellulose, and lignin.

A multi-species comparison of delta13C from whole wood, extractive-free wood and holocellulose.

The stable carbon (C) isotope composition (delta13C) of tree rings is a powerful metric for reconstructing past physiological responses to climate variation. However, accurate measurement and interpretation are complicated by diagenesis and the translocation of compounds with distinct isotopic signatures. Isolation and analysis of cellulose minimizes these complications by eliminating variation due to biosynthetic pathways; however, isolation of cellulose is time-consuming and has no clear endpoint. A faster and better-defined analytical method is desirable. Our objectives were to determine if there is a direct relationship between the isotopic compositions of whole wood (WW), whole wood treated with solvents to remove mobile extractives (extractive-free wood; EF) and holocellulose (HC) isolated by extractive removal and subsequent bleaching. We also determined if total C concentration could explain the isotopic composition and variation among these three wood components of each sample. A set of wood samples of diverse phylogeny, anatomy and chemical composition, was examined. The mean offset or difference between HC and EF delta13C was 1.07 +/- 0.09 per thousand and the offset between HC and WW was 1.32 +/- 0.10 per thousand. Equivalence tests (with alpha = 0.05) indicated that the relationship between EF delta13C and HC delta13C had a slope significantly similar to 1 +/- 5.5%, whereas for the WW delta13C: HC delta13C relationship, the slope was significantly similar to 1 +/- 10.08%. A regression model using EF delta13C to predict HC delta13C had a slope of 0.97, which was not significantly different from unity (P = 0.264), whereas the regression for WW had a slope of 0.92 which was significantly different from unity (P = 0.0098). Carbon concentration was correlated with HC:WW offset and cellulose:EF offset (P = 0.0501 and 0.007, respectively), but neither relationship explained much of the variation (r2 = 0.12 and 0.14, respectively). We suggest that HC extraction is unnecessary for most analyses of tree-ring delta13C; a simple solvent extraction is a suitable alternative for many applications.

Assessment of the adhesive properties of the bacterial polysaccharide FucoPol.

To address the industry's interest in finding novel biobased glues, the adhesive properties of the bacterial polysaccharide FucoPol were evaluated through shear bond strength tests. A FucoPol solution was used to bond different materials, namely, wood, glass, cardboard and cellulose acetate film. The shear strength was compared to that of the same adherends bonded with commercial synthetic glues. Wood-wood joints bonded with FucoPol formulation withstood 742.2±9.8kPa shear strength without detachment. FucoPol adhesive capacity for cardboard was comparable to that of the tested commercial glues (425±8.9kPa), yielding similar shear strength values (416.0±12.9kPa), while improved performance was shown for glass (115.1±26.2kPa) and cellulose acetate film (153.7±11.3kPa) comparing to the commercial glues (67.7-97.5kPa and 79.4-92.7kPa, respectively). This study demonstrates the adhesive properties of FucoPol, opening up the opportunity of using this bacterial polysaccharide for the development of new natural water-based glues, suitable to bond different materials.

Effect of ionic liquid treatment on the ultrastructural and topochemical features of compression wood in Japanese cedar (Cryptomeria japonica).

The morphological and topochemical changes in wood tissues in compression wood of Japanese cedar (Cryptomeria japonica) upon treated with two types of ionic liquids, 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]) and 1-ethylpyridinium bromide ([EtPy][Br]) were investigated. Compression wood tracheids were swollen by both ionic liquids but their swelling behaviors were different in the types of ionic liquids used. Under the polarized light, we confirmed that crystalline cellulose in compression wood is amorphized by [C2mim][Cl] treatment whereas it changes slightly by [EtPy][Br] treatment. Raman microscopic analyses revealed that [C2mim][Cl] can preferentially liquefy polysaccharides in compression wood whereas [EtPy][Br] liquefy lignin. In addition, the interaction of compression wood with ionic liquids is different for the morphological regions. These results will assist in the use of ionic liquid treatment of woody biomass to produce valuable chemicals, bio-fuels, bio-based composites and other products.

High consistency cellulase treatment of hardwood prehydrolysis kraft based dissolving pulp.

For enzymatic treatment of dissolving pulp, there is a need to improve the process to facilitate its commercialization. For this purpose, the high consistency cellulase treatment was conducted based on the hypothesis that a high cellulose concentration would favor the interactions of cellulase and cellulose, thus improves the cellulase efficiency while decreasing the water usage. The results showed that compared with a low consistency of 3%, the high consistency of 20% led to 24% increases of cellulase adsorption ratio. As a result, the viscosity decrease and Fock reactivity increase at consistency of 20% were enhanced from 510 mL/g and 70.3% to 471 mL/g and 77.6%, respectively, compared with low consistency of 3% at 24h. The results on other properties such as alpha cellulose, alkali solubility and molecular weight distribution also supported the conclusion that a high consistency of cellulase treatment was more effective than a low pulp consistency process.

Studying the effects of laccase treatment in a softwood dissolving pulp: cellulose reactivity and crystallinity.

An enzymatic biobleaching sequence (LVAQPO) using a laccase from Trametes villosa in combination with violuric acid (VA) and then followed by a pressurized hydrogen peroxide treatment (PO) was developed and found to give high bleaching properties and meet dissolving pulp requirements: high brightness, low content of hemicellulose, satisfactory pulp reactivity, no significant cellulose degradation manifested by α-cellulose and HPLC, and brightness stability against moist heat ageing. The incorporation of a laccase-mediator system (LMS) to bleach sulphite pulps can be a good alternative to traditional bleaching processes since thermogravimetric analysis (TGA) showed that the laccase treatment prevented the adverse effect of hydrogen peroxide on fibre surface as observed during a conventional hydrogen peroxide bleaching treatment (PO). Although VA exhibited the best results in terms of bleaching properties, the performance of natural mediators, such as p-coumaric acid and syringaldehyde, was discussed in relation to changes in cellulose surface detected by TGA.

Cationic polyacrylamide enhancing cellulase treatment efficiency of hardwood kraft-based dissolving pulp.

Cellulase treatment for decreasing viscosity and increasing Fock reactivity of dissolving pulp is a promising approach to reduce the use of toxic chemicals, such as hypochlorite in the dissolving pulp manufacturing process in the industry. Improving the cellulase treatment efficiency during the process is of practical interest. In the present study, the concept of using cationic polyacrylamide (CPAM) to enhance the cellulase treatment efficiency was demonstrated. This was mainly attributed to the increased cellulase adsorption onto cellulose fibers based on the patching/bridging mechanism. Results showed that the cellulase adsorption was increased by about 20% with the addition of 250 ppm of CPAM under the same conditions as those of the control. It was found that the viscosity decrease and Fock reactivity increase for the cellulase treatment was enhanced from using CPAM. The CPAM-assisted cellulase treatment concept may provide a practical alternative to the present hypochlorite-based technology for viscosity control in the industry.

Mimicking the Fenton reaction-induced wood decay by fungi for pretreatment of lignocellulose.

In this study, the Fenton reaction, which is naturally used by fungi for wood decay, was employed to pretreat rice straw and increase the enzymatic digestibility for the saccharification of lignocellulosic biomass. Using an optimized Fenton's reagent (FeCl3 and H2O2) for pretreatment, an enzymatic digestibility that was 93.2% of the theoretical glucose yield was obtained. This is the first report of the application of the Fenton reaction to lignocellulose pretreatment at a moderate temperature (i.e., 25°C) and with a relatively high loading of biomass (i.e., 10% (w/v)). Substantial improvement in the process economics of cellulosic fuel and chemical production can be achieved by replacing the conventional pretreatment with this Fenton-mimicking process.