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This article is a Commentary on Yu et al. (2024), 244: 1024–1040.

Summary: Polysaccharide structural complexity not only influences cell wall strength and extensibility but also hinders pathogenic and biotechnological attempts to saccharify the wall. In certain species and tissues, glucuronic acid side groups on xylan exhibit arabinopyranose or galactose decorations whose genetic and evolutionary basis is completely unknown, impeding efforts to understand their function and engineer wall digestibility.Genetics and polysaccharide profiling were used to identify the responsible loci in Arabidopsis and Eucalyptus from proposed candidates, while phylogenies uncovered a shared evolutionary origin. GH30‐family endo‐glucuronoxylanase activities were analysed by electrophoresis, and their differing specificities were rationalised by phylogeny and structural analysis.The newly identified xylan arabinopyranosyltransferases comprise an overlooked subfamily in the GT47‐A family of Golgi glycosyltransferases, previously assumed to comprise mainly xyloglucan galactosyltransferases, highlighting an unanticipated adaptation of both donor and acceptor specificities. Further neofunctionalisation has produced a Myrtaceae‐specific xylan galactosyltransferase. Simultaneously, GH30 endo‐glucuronoxylanases have convergently adapted to overcome these decorations, suggesting a role for these structures in defence. The differential expression of glucuronoxylan‐modifying genes across Eucalyptus tissues, however, hints at further functions.Our results demonstrate the rapid adaptability of biosynthetic and degradative carbohydrate‐active enzyme activities, providing insight into plant–pathogen interactions and facilitating plant cell wall biotechnological utilisation. See also the Commentary on this article by Mortimer & Scheller, 244: 749–751. [ABSTRACT FROM AUTHOR]

Abstract The present study deals with the production of cellulase-free endoxylanase by Aspergillus niger ISL-9 using wheat bran as a solid substrate. Endoxylanase was produced under a solid-state fermentation. Various growth parameters were optimized for the improved production of the enzyme. The Substrate level of 15 g was optimized as it provided the fungus with balanced aeration and nutrition. Among the six moisture contents investigated, Moisture Content 5 (MC5) was optimized (g/l: malt extract, 10; (NH4)2HPO4, 2.5; urea, 1.0) and 10 mL of MC5 was found to give the highest production of endoxylanase. The pH and time of incubation were optimized to 6.2 and 48 h respectively. The Inoculum size of 2 mL (1.4 × 106 spores/mL) gave the maximum enzyme production. After optimization of these growth parameters, a significantly high endoxylanase activity of 21.87 U/g was achieved. Very negligible Carboxymethylcellulase (CMCase) activity was observed indicating the production of cellulase-free endoxylanase. The notable finding is that the endoxylanase activity was increased by 1.4-fold under optimized conditions (p ≤ 0.05). The overall comparison of kinetic parameters for enhanced production of endoxylanase by A. niger ISL-9 under Solid State Fermentation (SSF) was also studied. Different kinetic variables which included specific growth rate, product yield coefficients, volumetric rates and specific rates were observed at 48, 72 and 96 h incubation time and were compared for MC1 and MC5. Among the kinetic parameters, the most significant result was obtained with volumetric rate constant for product formation (Qp) that was found to be optimum (1.89 U/h) at 72 h incubation period and a high value of Qp i.e.1.68 U/h was also observed at 48 h incubation period. Thus, the study demonstrates a cost-effective and environmentally sustainable process for xylanase production and exhibits scope towards successful industrial applications.

The present study deals with the production of cellulase-free endoxylanase by Aspergillus niger ISL-9 using wheat bran as a solid substrate. Endoxylanase was produced under a solid-state fermentation. Various growth parameters were optimized for the improved production of the enzyme. The Substrate level of 15 g was optimized as it provided the fungus with balanced aeration and nutrition. Among the six moisture contents investigated, Moisture Content 5 (MC5) was optimized (g/l: malt extract, 10; (NH4)2HPO4, 2.5; urea, 1.0) and 10 mL of MC5 was found to give the highest production of endoxylanase. The pH and time of incubation were optimized to 6.2 and 48 h respectively. The Inoculum size of 2 mL (1.4 × 106 spores/mL) gave the maximum enzyme production. After optimization of these growth parameters, a significantly high endoxylanase activity of 21.87 U/g was achieved. Very negligible Carboxymethylcellulase (CMCase) activity was observed indicating the production of cellulase-free endoxylanase. The notable finding is that the endoxylanase activity was increased by 1.4-fold under optimized conditions (p ≤ 0.05). The overall comparison of kinetic parameters for enhanced production of endoxylanase by A. niger ISL-9 under Solid State Fermentation (SSF) was also studied. Different kinetic variables which included specific growth rate, product yield coefficients, volumetric rates and specific rates were observed at 48, 72 and 96 h incubation time and were compared for MC1 and MC5. Among the kinetic parameters, the most significant result was obtained with volumetric rate constant for product formation (Qp) that was found to be optimum (1.89 U/h) at 72 h incubation period and a high value of Qp i.e.1.68 U/h was also observed at 48 h incubation period. Thus, the study demonstrates a cost-effective and environmentally sustainable process for xylanase production and exhibits scope towards successful industrial applications. [ABSTRACT FROM AUTHOR]

The valorization of lignocellulosic biomass, derived from various bio-waste materials, has received considerable attention as a sustainable approach to improve production chains while reducing environmental impact. Microbial enzymes have emerged as key players in the degradation of polysaccharides, offering versatile applications in biotechnology and industry. Among these enzymes, glycoside hydrolases (GHs) play a central role. Xylanases, in particular, are used in a wide range of applications and are essential for the production of xylose, which can be fermented into bioethanol or find use in many other industries. Currently, fungal secretomes dominate as the main reservoir of lignocellulolytic enzymes, but thermophilic microorganisms offer notable advantages in terms of enzyme stability and production efficiency. Here we present the genomic characterization of Geobacillus stearothermophilus GF16 to identify genes encoding putative enzymes involved in lignocellulose degradation. Thermostable GHs secreted by G. stearothermophilus GF16 were investigated and found to be active on different natural polysaccharides and synthetic substrates, revealing an array of inducible GH activities. In particular, the concentrated secretome possesses significant thermostable xylanase and β-xylosidase activities (5 ×103 U/L and 1.7 ×105 U/L, respectively), highlighting its potential for application in biomass valorization. We assessed the hemicellulose hydrolysis capabilities of various agri-food wastes using the concentrated secretome of the strain cultivated on xylan. An impressive 300-fold increase in xylose release compared to a commercially available cocktail was obtained with the secretome, underscoring the remarkable efficacy of this approach. [Display omitted] • Genome characterization of G. stearothermophilus GF16 reveals genes potentially involved in hemicellulose degradation. • The secretome of GF16 grown on a minimal medium enriched with 0.1 % xylan shows inducible xylanolytic properties. • G. stearothermophilus GF16 CAZymes are pivotal in converting agri-food wastes into value-added products, such as xylose. [ABSTRACT FROM AUTHOR]

Plant cell walls are largely composed of polysaccharide polymers, including cellulose, hemicelluloses (xyloglucan, xylan, mannan, and mixed-linkage β-1,3/1,4-glucan), and pectins. Among these cell wall polysaccharides, xyloglucan, xylan, mannan, and pectins are often O-acetylated, and polysaccharide O-acetylation plays important roles in cell wall assembly and disease resistance. Genetic and biochemical analyses have implicated the involvement of three groups of proteins in plant cell wall polysaccharide O-acetylation: trichome birefringence-like (TBL)/domain of unknown function 231 (DUF231), reduced wall acetylation (RWA), and altered xyloglucan 9 (AXY9). Although the exact roles of RWAs and AXY9 are yet to be identified, members of the TBL/DUF231 family have been found to be O-acetyltransferases responsible for the O-acetylation of xyloglucan, xylan, mannan, and pectins. Here, we provide a comprehensive overview of the occurrence of O-acetylated cell wall polysaccharides, the biochemical properties, structural features, and evolution of cell wall polysaccharide O-acetyltransferases, and the potential biotechnological applications of manipulations of cell wall polysaccharide acetylation. Further in-depth studies of the biochemical mechanisms of cell wall polysaccharide O-acetylation will not only enrich our understanding of cell wall biology, but also have important implications in engineering plants with increased disease resistance and reduced recalcitrance for biofuel production. [ABSTRACT FROM AUTHOR]

The transition towards a sustainable society involves the utilization of lignocellulosic biomass as a renewable feedstock for materials, fuel, and base chemicals. Lignocellulose consists of cellulose, hemicellulose, and lignin, forming a complex, recalcitrant matrix where efficient enzymatic saccharification is pivotal for accessing its valuable components. This study investigated microbial communities from brackish Lauwersmeer Lake, in The Netherlands, as a potential source of xylan-degrading enzymes. Environmental sediment samples were enriched with wheat arabinoxylan (WAX) and beechwood glucuronoxylan (BEX), with enrichment on WAX showing higher bacterial growth and complete xylan degradation compared to BEX. Metagenomic sequencing revealed communities consisting almost entirely of bacteria (>99%) and substantial shifts in composition during the enrichment. The first generation of seven-day enrichments on both xylans led to a high accumulation of Gammaproteobacteria (49% WAX, 84% BEX), which were largely replaced by Alphaproteobacteria (42% WAX, 69% BEX) in the fourth generation. Analysis of the protein function within the sequenced genomes showed elevated levels of genes associated with the carbohydrate catabolic process, specifically targeting arabinose, xylose, and xylan, indicating an adaptation to the primary monosaccharides present in the carbon source. The data open up the possibility of discovering novel xylan-degrading proteins from other sources aside from the thoroughly studied Bacteroidota. [ABSTRACT FROM AUTHOR]

Bifidobacteria are commonly encountered members of the human gut microbiota that possess the enzymatic machinery necessary for the metabolism of certain plant-derived, complex carbohydrates. In the current study we describe differential growth profiles elicited by a panel of 21 newly isolated Bifidobacterium pseudocatenulatum strains on various plant-derived glycans. Using a combination of gene-trait matching and comparative genome analysis, we identified two distinct xylanases responsible for the degradation of xylan. Furthermore, three distinct extracellular α-amylases were shown to be involved in starch degradation by certain strains of B. pseudocatenulatum. Biochemical characterization showed that all three a-amylases can cleave the related substrates amylose, amylopectin, maltodextrin, glycogen and starch. The genes encoding these enzymes are variably found in the species B. pseudocatenulatum, therefore constituting a strain-specific adaptation to the gut environment as these glycans constitute common plant-derived carbohydrates present in the human diet. Overall, our study provides insights into the metabolism of these common dietary carbohydrates by a human-derived bifidobacterial species. [ABSTRACT FROM AUTHOR]

Abstract Dinizia Excelsa is an Amazonian tree with a wide range of applications as a raw material in the industry. The objective of this study was to extract, characterize, and evaluate the biological activities of xylan extracted from Dinizia excelsa wood. The xylan was obtained in five stages, including delignification, precipitation, purification, and freeze-drying. The physicochemical analysis of xylan included the determination of monosaccharides, elemental composition, FTIR analysis, 2D nuclear magnetic resonance spectroscopy, and the determination of molecular weight. Xylan had an extraction yield of 28.44% and an elemental composition of 35.03% carbon, 5.65% hydrogen, and 59.32% oxygen. FTIR analysis revealed similarities between Dinizia excelsa xylan and commercial xylan. 2D NMR analysis confirmed the presence of characteristic xylan groups. Furthermore, xylan has a low molecular weight. In vitro cytotoxicity tests demonstrated low toxicity, indicating its potential for biological applications. Immunomodulatory activity assays revealed that xylan stimulated cell proliferation and the production of anti-inflammatory cytokines. The anticoagulant activity of xylan was low compared to heparin. The antioxidant activity of xylan was weaker compared to ascorbic acid and butylated hydroxytoluene (BHT). These results indicate that xylan from Dinizia excelsa has potential for several biomedical applications due to its immunomodulatory and anticoagulant properties.

Hemicellulose is one of the most important natural polysaccharides in nature. Hemicellulose from different sources varies in chemical composition and structure, which in turn affects the modification effects and industrial applications. Grain and oil by-products (GOBPs) are important raw materials for hemicellulose. This article reviews the modification methods of hemicellulose in GOBPs. The effects of chemical and physical modification methods on the properties of GOBP hemicellulose biomaterials are evaluated. The potential applications of modified GOBP hemicellulose are discussed, including its use in film production, hydrogel formation, three-dimensional (3D) printing materials, and adsorbents for environmental remediation. The limitations and future recommendations are also proposed to provide theoretical foundations and technical support for the efficient utilization of these by-products. [ABSTRACT FROM AUTHOR]

Fluorescent sensors with single reading are generally subject to unpredictable disturbs from environmental and artificial factors. In order to overcome this barrier of detection reliability, a paper-based optical sensor with proportional fluorescence was established and further combined with a smartphone for visual, on-site and quantitative detection of Fe3+, which affects the color, smell and taste of water, and endangers the health of plants and animals. The ratio fluorescent probe was fabricated by rhodamine B and carbon quantum dots derived from xylan. The red fluorescence of rhodamine B was inert to Fe3+, which was referred to as background. And blue emitting carbon quantum dots functioned as signal report units, which would be quenched by Fe3+ and make the fluorescence of the ratio probe change from purple to red. The quantitative detection of Fe3+ was conducted by investigating the RGB value of fluorescent images with a smartphone. With the increase of Fe3+ concentration, the R/B (red/blue) value of the fluorescent paper gradually increased. The linear detection range was 10–180 μM, and the limit of detection was 198.2 nM. The application of ratio fluorescent paper with a smartphone provides a facile method for the rapid detection of ions. [ABSTRACT FROM AUTHOR]

In this study, the α-glucosidase (maltase-glucoamylase: MGAM) and α-amylase inhibitory properties elicited by xylooligosaccharides (XOSs) prepared from dulse xylan were analysed as a potential mechanism to control postprandial hyperglycaemia for type-2 diabetes prevention and treatment. Xylan was purified from red alga dulse powder and used for enzymatic hydrolysis using Sucrase X to produce XOSs. Fractionation of XOSs produced xylobiose (X2), β-(1→3)-xylosyl xylobiose (DX3), xylotriose (X3), β-(1→3)-xylosyl-xylotriose (DX4), and a dulse XOS mixture with n ≥ 4 xylose units (DXM). The different fractions exhibited moderate MGAM (IC50 = 11.41–23.44 mg/mL) and α-amylase (IC50 = 18.07–53.04 mg/mL) inhibitory activity, which was lower than that of acarbose. Kinetics studies revealed that XOSs bound to the active site of carbohydrate digestive enzymes, limiting access to the substrate by competitive inhibition. A molecular docking analysis of XOSs with MGAM and α-amylase clearly showed moderate strength of interactions, both hydrogen bonds and non-bonded contacts, at the active site of the enzymes. Overall, XOSs from dulse could prevent postprandial hyperglycaemia as functional food by a usual and continuous consumption. [ABSTRACT FROM AUTHOR]

Bifidobacteria are commonly encountered members of the human gut microbiota that possess the enzymatic machinery necessary for the metabolism of certain plant-derived, complex carbohydrates. In the current study we describe differential growth profiles elicited by a panel of 21 newly isolated Bifidobacterium pseudocatenulatum strains on various plant-derived glycans. Using a combination of gene-trait matching and comparative genome analysis, we identified two distinct xylanases responsible for the degradation of xylan. Furthermore, three distinct extracellular α-amylases were shown to be involved in starch degradation by certain strains of B. pseudocatenulatum. Biochemical characterization showed that all three α-amylases can cleave the related substrates amylose, amylopectin, maltodextrin, glycogen and starch. The genes encoding these enzymes are variably found in the species B. pseudocatenulatum, therefore constituting a strain-specific adaptation to the gut environment as these glycans constitute common plant-derived carbohydrates present in the human diet. Overall, our study provides insights into the metabolism of these common dietary carbohydrates by a human-derived bifidobacterial species.

Growth suppression and defence signalling are simultaneous strategies that plants invoke to respond to abiotic stress. Here, we show that the drought stress response of poplar trees (Populus trichocarpa) is initiated by a suppression in cell wall derived methanol (MeOH) emissions and activation of acetic acid (AA) fermentation defences. Temperature sensitive emissions dominated by MeOH (AA/MeOH

Corn as one of the world's major food crops, its by-product corn cob is also rich in resources. However, the unreasonable utilization of corn cob often causes the environmental pollution, waste of resources and other problems. As one of the most abundant polymers in nature, xylan is widely used in food, medicine, materials and other fields. Corn cob is rich in xylan, which is an ideal raw material for extracting xylan. However, the intractable lignin is covalently linked to xylan, which increases the difficulty of xylan extraction. It has been reported that the deep eutectic solvent (DES) could preferentially dissolve lignin in biomass, thereby dissolving the xylan. Then, the xylan in the extract was separated by ethanol precipitation method. The xylan precipitate was obtained after centrifugation, while the supernatant was retained. The components of the supernatant after ethanol precipitation were separated by the rotary evaporator. The ethanol, water and DES were collected for the subsequent extraction of corn cob xylan. In this study, a novel way was provided for the green production of corn cob xylan. The DES was used to extract xylan from corn cob which was used as the raw material. The effects of solid-liquid ratio, reaction time, reaction temperature and water content of DES on the extraction rate of corn cob xylan were investigated by the single factor test. Furthermore, the orthogonal test was designed to optimize the xylan extraction process. The structure of corn cob xylan was analyzed and verified. The results showed that the optimum extraction conditions of corn cob xylan were as follows: the ratio of corn cob to DES was 1 : 15 (g : mL), the extraction time was 3 h, the extraction temperature was 60 °C, and the water content of DES was 70%. Under these conditions, the extraction rate of xylan was 16.46%. The extracted corn cob xylan was distinctive triple helix of polysaccharide, which was similar to the structure of commercially available xylan. Xylan was effectively and workably extracted from corn cob by the DES method. This study provided a new approach for high value conversion of corn cob and the clean production of xylan.

Abstract Reduced graphene oxide (rGO) films suffer from low capacitance for inner unreduced oxygen functional groups, restacking of sheets and high contact resistance. Herein, carbon spheres derived from renewable xylan were added to graphene oxide with large sheet area to fabricate film by gelation and filtration, followed by in situ reduction for high-performance flexible supercapacitor. rGO film with transverse size about 13 μm showed a good specific capacitance of 967 mF/cm2 at a scanning rate of 5 mV/s and increased to 1786 mF/cm2 by in situ reducing its inner part, which generally remained oxidized due to outer hindering from hydrophobic graphene. Then, by hydrothermal carbonization of xylan and activation with KOH, activated carbon sphere (aXCS) was prepared, which had a diameter of 150–200 nm and a specific capacitance of 270 F/g. The aXCS acted as spacer and connector to avoid restacking of graphene sheets and decrease interlayer contact resistance, resulting 94% increase in capacitance performance from rGO film to aXCS/rGO film. Therefore, combined in situ reduction and enhancement through compositing aXCS, the final film (aXCS/rGO-AA) showed a boosted specific capacitance of 755 mF/cm2 at 1 mA/cm2 in double electrode system, power density of 22.5–2250 mW/cm2, and energy density of 11.88–25.2 mWh/cm2. Meanwhile, aXCS/rGO-AA had outstanding cycling stability that its specific capacitance maintained 108.7% after 10,000 cycles of charge–discharge, showing promising potential in wearable and portable electronics. Graphical abstract

Abstract Background The abundance of glucuronoxylan (GX) in agricultural and forestry residual side streams positions it as a promising feedstock for microbial conversion into valuable compounds. By engineering strains of the widely employed cell factory Saccharomyces cerevisiae with the ability to directly hydrolyze and ferment GX polymers, we can avoid the need for harsh chemical pretreatments and costly enzymatic hydrolysis steps prior to fermentation. However, for an economically viable bioproduction process, the engineered strains must efficiently express and secrete enzymes that act in synergy to hydrolyze the targeted polymers. Results The aim of this study was to equip the xylose-fermenting S. cerevisiae strain CEN.PK XXX with xylanolytic enzymes targeting beechwood GX. Using a targeted enzyme approach, we matched hydrolytic enzyme activities to the chemical features of the GX substrate and determined that besides endo-1,4-β-xylanase and β-xylosidase activities, α-methyl-glucuronidase activity was of great importance for GX hydrolysis and yeast growth. We also created a library of strains expressing different combinations of enzymes, and screened for yeast strains that could express and secrete the enzymes and metabolize the GX hydrolysis products efficiently. While strains engineered with BmXyn11A xylanase and XylA β-xylosidase could grow relatively well in beechwood GX, strains further engineered with Agu115 α-methyl-glucuronidase did not display an additional growth benefit, likely due to inefficient expression and secretion of this enzyme. Co-cultures of strains expressing complementary enzymes as well as external enzyme supplementation boosted yeast growth and ethanol fermentation of GX, and ethanol titers reached a maximum of 1.33 g L− 1 after 48 h under oxygen limited condition in bioreactor fermentations. Conclusion This work underscored the importance of identifying an optimal enzyme combination for successful engineering of S. cerevisiae strains that can hydrolyze and assimilate GX. The enzymes must exhibit high and balanced activities, be compatible with the yeast’s expression and secretion system, and the nature of the hydrolysis products must be such that they can be taken up and metabolized by the yeast. The engineered strains, particularly when co-cultivated, display robust growth and fermentation of GX, and represent a significant step forward towards a sustainable and cost-effective bioprocessing of GX-rich biomass. They also provide valuable insights for future strain and process development targets.

Abstract Background The recently discovered PcAA14A and B from white-rot basidiomycete Pycnoporus coccineus enriched our understanding of the oxidative degradation of xylan in fungi, however, the unusual mode of action of AA14 LPMOs has sparked controversy. The substrate specificity and functionality of AA14 LPMOs still remain enigmatic and need further investigation. Results In this study, a novel AA14 LPMO was characterized from the ascomycete Talaromyces rugulosus. TrAA14A has a broad substrate specificity with strong oxidative activity on pure amorphous cellulose and xyloglucan. It could simultaneously oxidize cellulose, xylan and xyloglucan in natural hemi/cellulosic substrate such as fibrillated eucalyptus pulp, and released native and oxidized cello-oligosaccharides, xylo-oligosaccharides and xyloglucan oligosaccharides from this substrate, but its cellulolytic/hemicellulolytic activity became weaker as the contents of xylan increase in the alkaline-extracted hemi/cellulosic substrates. The dual cellulolytic/hemicellulolytic activity enables TrAA14A to possess a profound boosting effect on cellulose hydrolysis by cellulolytic enzymes. Structure modelling of TrAA14A revealed that it exhibits a relatively flat active-site surface similar to the active-site surfaces in AA9 LPMOs but quite distinct from PcAA14B, despite TrAA14A is strongly clustered together with AA14 LPMOs. Remarkable difference in electrostatic potentials of L2 and L3 surfaces was also observed among TrAA14A, PcAA14B and NcLPMO9F. We speculated that the unique feature in substrate-binding surface might contribute to the cellulolytic/hemicellulolytic activity of TrAA14A. Conclusions The extensive cellulolytic/hemicellulolytic activity on natural hemi/cellulosic substrate indicated that TrAA14A from ascomycete is distinctively different from previously characterized xylan-active AA9 or AA14 LPMOs. It may play as a bifunctional enzyme to decompose some specific network structures formed between cellulose and hemicellulose in the plant cell walls. Our findings shed new insights into the novel substrate specificities and biological functionalities of AA14 LPMOs, and will contribute to developing novel bifunctional LPMOs as the booster in commercial cellulase cocktails to efficiently break down the hemicellulose-cellulose matrix in lignocellulose.

Summary: There is an increasing need for renewable energy sources to replace part of our fossil fuel‐based economy and reduce greenhouse gas emission. Sugarcane bagasse is a prominent feedstock to produce cellulosic bioethanol, but strategies are still needed to improve the cost‐effective exploitation of this potential energy source. In model plants, it has been shown that GUX genes are involved in cell wall hemicellulose decoration, adding glucuronic acid substitutions on the xylan backbone. Mutation of GUX genes increases enzyme access to cell wall polysaccharides, reducing biomass recalcitrance in Arabidopsis thaliana. Here, we characterized the sugarcane GUX genes and silenced GUX2 in commercial hybrid sugarcane. The transgenic lines had no penalty in development under greenhouse conditions. The sugarcane GUX1 and GUX2 enzymes generated different patterns of xylan glucuronidation, suggesting they may differently influence the molecular interaction of xylan with cellulose and lignin. Studies using biomass without chemical or steam pretreatment showed that the cell wall polysaccharides, particularly xylan, were less recalcitrant in sugarcane with GUX2 silenced than in WT plants. Our findings suggest that manipulation of GUX in sugarcane can reduce the costs of second‐generation ethanol production and enhance the contribution of biofuels to lowering the emission of greenhouse gases. [ABSTRACT FROM AUTHOR]

Spent mushroom substrate (SMS), a lignocellulosic waste after mushroom production is generally discarded without proper management. There is increasing interest in the sustainable transformation of lignocellulosic waste into high-value products. Within this context, the present study investigated the potential of the SMS from the cultivation of Pleurotus pulmonarius and Auricularia auricula on rubber tree wood sawdust as substrates for xylooligosaccharides (XOS) production. SMS samples from these two edible mushrooms were extracted using alkaline xylan extraction, producing maximum true recovery amounts of xylan in the range 34.61%–37.49% using 18% NaOH at 70 °C for 3 h. Production of XOS from alkaline-extracted xylan from the SMS samples of both mushroom species using economically crude xylanases from Aspergillus flavus KUB2 resulted in XOS (X2–X5) production of 241.47–249.04 mg/g, with X3 as the predominant XOS product. The produced XOS had excellent prebiotic activity and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and contained high total phenolic contents. The combined beneficial bioactivities in terms of prebiotic and antioxidant properties suggested that the XOS produced from sawdust-based SMS samples of P. pulmonarius and A. auricula could be promising ingredients for both food and pharmaceutical applications. [ABSTRACT FROM AUTHOR]

Lignocellulose, the most abundant and renewable plant resource, is a complex of polymers mainly composed of polysaccharides (cellulose and hemicelluloses) and an aromatic polymer (lignin). Utilisation of lignocellulosic biomass for biotechnological applications has increased over the past few years. Xylan is the second most abundant carbohydrate in plant cell walls, and structurally, it is a heteropolysaccharide with a backbone composed of β-1,4-d-xylopyranosyl units connected with glycosidic bonds. Xylanases degrade this complex structure of xylan and can be produced by various microorganisms, including fungi, bacteria, and yeasts. Lignocellulosic biomass is the most economical substrate for the production of fungal xylanases. The bioconversion of lignocellulosic biomass to industrially important products, i.e., xylooligosaccharides and biofuels, is possible via the application of xylanases. These enzymes also play a key role in enhancing the nutrition of food and feed and the bio-bleaching of paper and kraft pulp. However, the demand for more potent and efficient xylanases with high activity has increased, which is fulfilled by involving recombinant DNA technology. Hence, in this review, we thoroughly discussed the biotechnological potential of lignocellulosic biomass for the production of fungal xylanases, their purification, molecular strategies for improving their efficiency, and their utilisation for the production of valuable products and in other industrial processes. [ABSTRACT FROM AUTHOR]

Fermentation of dietary fiber (DF) is beneficial for gut health, but its prebiotic effects are often impeded in the distal large intestine because of the fast degradation of fermentable substrates. One way to enhance the prebiotic effect of DF is to deliver fibers to the lower parts of the gut, which can be achieved by mixing different kinds of fiber. Therefore, in the present study, an ileum-cannulated pig model was employed to investigate the fermentation influence in the large intestine by infusing resistant starch solely (RS, fast fermentable fiber) and mixing with other fibers (xylan or cellulose). Twenty-four ileum-cannulated growing pigs were divided into four groups: one control group receiving saline ileal infusions and three experimental groups infused with RS, RS with xylan, or RS with cellulose. Fecal and plasma samples were analyzed for gut microbiota composition, short-chain fatty acids (SCFAs), and blood biochemistry. Results indicated no significant differences between the RS and control group for the microbiome and SCFA concentration (p > 0.05). However, RS combined with fibers, particularly xylan, resulted in enhanced and prolonged fermentation, marked by an increase in Blautia and higher lactate and acetate production (p < 0.05). In contrast, RS with cellulose infusion enriched bacterial diversity in feces (p < 0.05). Blood biochemistry parameters showed no significant differences across groups (p > 0.05), though a trend of increased glucose levels was noted in the treatment groups (p < 0.1). Overall, RS alone had a limited impact on the distal hindgut microbiota due to rapid fermentation in the proximal gut, whereas combining RS with other fibers notably improved gut microecology by extending the fermentation process. [ABSTRACT FROM AUTHOR]

In order to improved the defects of xylan-based films such as strong hygroscopicity and low mechanical strength, a collaborative modification protocol of citric acid (CA) and MPTMS-modified xylan (MSMX) was proposed. Xylan from sugarcane bagasse was firstly modified by (3-mercaptopropyl)trimethoxysilane (MPTMS), and then citric acid was used as crosslinking agent or plasticizer. The MSMX/PVA/CA films were prepared by casting method and the effects of citric acid content on the structure and packaging performance of the composite film were studied. The results show that with the increase of CA content, the cross-linking degree of MSMX/PVA/CA films increases and the internal structure becomes more dense, which lead to the significant enhancement of mechanical properties and water vapor barrier performance. Meanwhile, the hydrophobicity of the MSMX/PVA/CA films is improved with the decrease of hydrophilice groups. When CA content is 20% (mass fraction), the tensile strength of MSMX/PVA/CA film is 41.8 MPa, water contact angle is 82°, and the water vapor transmittance reaches 2.79×10-13 g·cm·cm-2·s-1·Pa-1, which is 37.79% lower than that of film without CA. The addition of CA improves the moisture barrier properties and mechanical strength of xylan composite films, which makes it have a potential application in the field of food and drug packaging.

The transition towards a sustainable society involves the utilization of lignocellulosic biomass as a renewable feedstock for materials, fuel, and base chemicals. Lignocellulose consists of cellulose, hemicellulose, and lignin, forming a complex, recalcitrant matrix where efficient enzymatic saccharification is pivotal for accessing its valuable components. This study investigated microbial communities from brackish Lauwersmeer Lake, in The Netherlands, as a potential source of xylan-degrading enzymes. Environmental sediment samples were enriched with wheat arabinoxylan (WAX) and beechwood glucuronoxylan (BEX), with enrichment on WAX showing higher bacterial growth and complete xylan degradation compared to BEX. Metagenomic sequencing revealed communities consisting almost entirely of bacteria (>99%) and substantial shifts in composition during the enrichment. The first generation of seven-day enrichments on both xylans led to a high accumulation of Gammaproteobacteria (49% WAX, 84% BEX), which were largely replaced by Alphaproteobacteria (42% WAX, 69% BEX) in the fourth generation. Analysis of the protein function within the sequenced genomes showed elevated levels of genes associated with the carbohydrate catabolic process, specifically targeting arabinose, xylose, and xylan, indicating an adaptation to the primary monosaccharides present in the carbon source. The data open up the possibility of discovering novel xylan-degrading proteins from other sources aside from the thoroughly studied Bacteroidota.

Plant cell walls are largely composed of polysaccharide polymers, including cellulose, hemicelluloses (xyloglucan, xylan, mannan, and mixed-linkage β-1,3/1,4-glucan), and pectins. Among these cell wall polysaccharides, xyloglucan, xylan, mannan, and pectins are often O-acetylated, and polysaccharide O-acetylation plays important roles in cell wall assembly and disease resistance. Genetic and biochemical analyses have implicated the involvement of three groups of proteins in plant cell wall polysaccharide O-acetylation: trichome birefringence-like (TBL)/domain of unknown function 231 (DUF231), reduced wall acetylation (RWA), and altered xyloglucan 9 (AXY9). Although the exact roles of RWAs and AXY9 are yet to be identified, members of the TBL/DUF231 family have been found to be O-acetyltransferases responsible for the O-acetylation of xyloglucan, xylan, mannan, and pectins. Here, we provide a comprehensive overview of the occurrence of O-acetylated cell wall polysaccharides, the biochemical properties, structural features, and evolution of cell wall polysaccharide O-acetyltransferases, and the potential biotechnological applications of manipulations of cell wall polysaccharide acetylation. Further in-depth studies of the biochemical mechanisms of cell wall polysaccharide O-acetylation will not only enrich our understanding of cell wall biology, but also have important implications in engineering plants with increased disease resistance and reduced recalcitrance for biofuel production.

BackgroundThe development of bioenergy crops with reduced recalcitrance to enzymatic degradation represents an important challenge to enable the sustainable production of advanced biofuels and bioproducts. Biomass recalcitrance is partly attributed to the complex structure of plant cell walls inside which cellulose microfibrils are protected by a network of hemicellulosic xylan chains that crosslink with each other or with lignin via ferulate (FA) bridges. Overexpression of the rice acyltransferase OsAT10 is an effective bioengineering strategy to lower the amount of FA involved in the formation of cell wall crosslinks and thereby reduce cell wall recalcitrance. The annual crop sorghum represents an attractive feedstock for bioenergy purposes considering its high biomass yields and low input requirements. Although we previously validated the OsAT10 engineering approach in the perennial bioenergy crop switchgrass, the effect of OsAT10 expression on biomass composition and digestibility in sorghum remains to be explored.ResultsWe obtained eight independent sorghum (Sorghum bicolor (L.) Moench) transgenic lines with a single copy of a construct designed for OsAT10 expression. Consistent with the proposed role of OsAT10 in acylating arabinosyl residues on xylan with p-coumarate (pCA), a higher amount of p-coumaroyl-arabinose was released from the cell walls of these lines upon hydrolysis with trifluoroacetic acid. However, no major changes were observed regarding the total amount of pCA or FA esters released from cell walls upon mild alkaline hydrolysis. Certain diferulate (diFA) isomers identified in alkaline hydrolysates were increased in some transgenic lines. The amount of the main cell wall monosaccharides glucose, xylose, and arabinose was unaffected. The transgenic lines showed reduced lignin content and their biomass released higher yields of sugars after ionic liquid pretreatment followed by enzymatic saccharification.ConclusionsExpression of OsAT10 in sorghum leads to an increase of xylan-bound pCA without reducing the overall content of cell wall FA esters. Nevertheless, the amount of total cell wall pCA remains unchanged indicating that most pCA is ester-linked to lignin. Unlike other engineered plants overexpressing OsAT10 or a phylogenetically related acyltransferase with similar putative function, the improvements of biomass saccharification efficiency in sorghum OsAT10 lines are likely the result of lignin reductions rather than reductions of cell wall-bound FA. These results also suggest a relationship between xylan-bound pCA and lignification in cell walls.

The recombinant 40 kDa BoExXyl43A glycoside hydrolase family 43 (GH43) from bacterium Bacteroides ovatus exhibited highest specific activity (U/mg) against corn cob xylan (136.8), followed by Beechwood xylan (81.1), Carbosynth xylan (69.3), 4-O-D-methylglucuronoxylan (61.4) and Birchwood xylan (59.9). BoExXyl43A demonstrated optimal performance at 37 °C and pH 7.6 with Vmax and Km of 141.8 U/mg and 4.0 mg/mL as well as 64.1 U/mg and 6.0 mg/mL against corn cob and Birchwood xylan, respectively. The activity of BoExXyl43A increased by 48 % by addition of 10 mM Ca2+ ions, while 1 mM EDTA or 1 mM EGTA decreased its activity by 100 % or 42.5 %, respectively, highlighting its calcium-ion dependence. Thin-layer chromatography (TLC) analysis of BoExXyl43A hydrolysates of Birchwood and Beechwood xylan as well as that of various xylooligosaccharides (DP2-DP9) from corn cob xylan showed the release of D-xylose, identifying it as an exo-β-1,4-xylosidase/exo-β-1,4-xylanase (EC 3.2.1.-/3.2.1.37). Moreover, the time-dependent TLC analysis of xylobiose hydrolysis showed release of D-xylose units, confirming its β-xylosidase activity. BoExXyl43A also exhibited exo-1,4-β-xylosidase activity on Larchwood and Carbosynth xylans. Notably, it released D-xylose from α-L-Araf2-xylotriose demonstrating its activity against decorated xylooligosaccharides. BoExXyl43A's exo-1,4-β-xylosidase and residual β-xylosidase activity on xylan and xylobiose, respectively, could potentially enhance xylan saccharification efficiency in bioethanol-based refineries. The molecular modeling showed that BoExXyl43A has 5-bladed β-propeller structure with a very shallow active-site having −1, +1 and + 2 subsites, which could accommodate three D-xylose units of longer xylan like xylododecaose thus supporting its exoxylosidase activity.

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Kozo paper, usu-mino-gami, is frequently used as the first back lining paper of hanging scrolls in order to support the main paper with a painting or a work of calligraphy on it. To dye it an appropriate color, paper is often treated with an alkali mordant solution. However, current kozo paper products have received such comments from conservators that wet tensile strength is weak and hard to handle. Therefore, improving the wet tensile strength of kozo paper is required. In previous papers, the effect of the sheet forming method, cooking condition, and parenchyma cell content between fibers on the wet tensile strength of kozo paper has been investigated. In this paper, the effect of glucuronoxylan, the main component of hardwood hemicellulose on the wet tensile strength of kozo paper was investigated. The wet tensile strength of kozo paper, when made in different cooking conditions, was evaluated using the Finch device. Glucuronoxylan content in fiber was analyzed using GC-FID. According to the results, it has been proved that glucuronoxylan content (with a xylan to glucan molar ratio of 4.43% to 5.16%) itself contributes to the wet tensile strength of the kozo sheet. Therefore, to increase the wet tensile strength of kozo paper, it is recommended to cook under milder conditions, thus retaining a higher amount of glucuronoxylan in the pulp. [ABSTRACT FROM AUTHOR]

Adsorption is one of the most significant approaches for treatment of wastewater. An adsorbent with high mechanical strength, good renewability, and high efficiency is expected for practical applications. In this paper, a cationic xylan-based aerogel composed of xylan, polyvinyl alcohol, and agarose was fabricated to adsorb pectin, which is a typical anionic trash substance in the papermaking white water. The freeze-drying method was used to prepare the aerogel. A cationic xylan-based aerogel with high mechanical strength (34.676 MPa at 50% strain) was obtained. FT-IR results illustrated that the hydrogen bonds between three components contributed to the formation of aerogels. The addition of cationic xylan led to a slight decrease of crystallinity and thermostability of the aerogels. The maximum adsorption capacity of anionic pectin was 19.52 mg/g. Moreover, the aerogels maintained a high pectin-adsorption capacity after five recycles. This new cationic xylan-based aerogel offers potential possibilities for the development of value-added hemicellulose-based materials and the purification of papermaking white water in practical applications.

Sugarcane bagasse is a rich source for Hemicelluloses. Xylan is a major type of hemicellulose represented as glucurono- arabinoxylans (GAX) in sugarcane. In the present study, comparative analysis of different xylan extraction methods namely sodium borohydride treatment, dimethyl sulfoxide (DMSO) extraction; dilute acid treatment, sonication, hydrogen peroxide and hot water treatment methods have been carried out for extraction and purification xylan from the bagasse of sugarcane genotypes Co 86032, Co 2001 -15, SES 159, and SES 18. The results showed that alkaline extracted sugarcane bagasse yielded significantly highest xylan yield and recovery in the range of 23.85-32.35% and 72.37%-97% respectively as compared to the rest of the pretreatment methods. Moderate xylan yield (7.68-17.43%) and recovery (22.49-52.89%) was observed using hot water, sodium borohydride and hydrogen peroxide pretreatment methods with significantly highest xylan recovery of 52.89% in hydrogen peroxide pretretated bagasse. Among all the pretreatment methods studied, DMSO, dilute acid and sonication pretreated bagasse samples yielded significantly very low xylan recovery in the range of 1.21-4.89%. Fourier Transmission Infra-Red (FT-IR) spectroscopic analysis of alkali extracted xylan showed similar spectral profile of commercial Beechwood xylan and indicated the presence of hemicellulose structures. These results evidenced the simple economically feasible xylan extraction technology and provided much more scope for using sugarcane bagasse as potential xylan source to produce industrially important value added products.

Agricultural and animal farming practices contribute significantly to greenhouse gas (GHG) emissions such as NH3, CH4, CO2, and NOx, causing local environmental concerns involving health risks and water/air pollution. A growing need to capture these pollutants is leading to the development of new strategies, including the use of solid adsorbents. However, commonly used adsorbent materials often pose toxicity and negative long-term environmental effects. This study aimed to develop responsive eco-friendly cryogels using xylan extracted from coffee parchment, a typical residue from coffee production. The crosslinking in cryogels was accomplished by “freeze-thawing” and subsequent freeze-drying. Cryogels were characterized in terms of morphology by using scanning electron microscopy, porosity, and density by the liquid saturation method and also moisture adsorption and ammonia adsorption capacity. The analysis showed that the porosity in the cryogels remained around 0.62–0.42, while the apparent densities varied from 0.14 g/cm3 to 0.25 g/cm3. The moisture adsorption capacity was the highest at the highest relative humidity level (80%), reaching 0.25–0.43 g of water per gram of sample; the amount of water adsorbed increased when the xylan content in the cryogel increased up to 10% w/v, which was consistent with the hygroscopic nature of xylan. The ammonia adsorption process was modeled accurately by a pseudo-second-order equation, where the maximum adsorption capacity in equilibrium reached 0.047 mg NH3/g when xylan reached 10% w/v in cryogels, indicating a chemisorption process. The cryogels under investigation hold promise for ammonia adsorption applications and GHG separation, offering a sustainable alternative for gas-capturing processes.

Fluorescent sensors with single reading are generally subject to unpredictable disturbs from environmental and artificial factors. In order to overcome this barrier of detection reliability, a paper-based optical sensor with proportional fluorescence was established and further combined with a smartphone for visual, on-site and quantitative detection of Fe3+, which affects the color, smell and taste of water, and endangers the health of plants and animals. The ratio fluorescent probe was fabricated by rhodamine B and carbon quantum dots derived from xylan. The red fluorescence of rhodamine B was inert to Fe3+, which was referred to as background. And blue emitting carbon quantum dots functioned as signal report units, which would be quenched by Fe3+ and make the fluorescence of the ratio probe change from purple to red. The quantitative detection of Fe3+ was conducted by investigating the RGB value of fluorescent images with a smartphone. With the increase of Fe3+ concentration, the R/B (red/blue) value of the fluorescent paper gradually increased. The linear detection range was 10–180 μM, and the limit of detection was 198.2 nM. The application of ratio fluorescent paper with a smartphone provides a facile method for the rapid detection of ions.

ABSTRACTBifidobacteria are prominent members of the human gut microbiota throughout life. The ability to utilize milk- and plant-derived carbohydrates is important for bifidobacterial colonization of the infant and adult gut. The Bifidobacterium catenulatum subspecies kashiwanohense (B. kashiwanohense) was originally isolated from infant feces. However, only a few strains have been described, and the characteristics of this subspecies have been poorly investigated. Here, we characterized genotypes and phenotypes of 23 B. kashiwanohense-associated strains, including 12 newly sequenced isolates. Genome-based analysis clarified the phylogenetic relationship between these strains, revealing that only 13 strains are genuine B. kashiwanohense. We defined specific marker sequences and investigated the worldwide prevalence of B. kashiwanohense based on metagenome data. This revealed that not only infants but also adults and weaning children harbor this subspecies in the gut. Most B. kashiwanohense strains utilize long-chain xylans and possess genes for extracellular xylanase (GH10), arabinofuranosidase and xylosidase (GH43), and ABC transporters that contribute to the utilization of xylan-derived oligosaccharides. We also confirmed that B. kashiwanohense strains utilize short- and long-chain human milk oligosaccharides and possess genes for fucosidase (GH95 and GH29) and specific ABC transporter substrate-binding proteins that contribute to the utilization of a wide range of human milk oligosaccharides. Collectively, we found that B. kashiwanohense strains utilize both plant- and milk-derived carbohydrates and identified key genetic factors that allow them to assimilate various carbohydrates.

In an attempt to enhance the value of sugarcane leaf, xylan was extracted and used for xylooligosaccharide (XO) production via enzymatic hydrolysis using xylanase from the black yeast Aureobasidium pullulans. The xylan was extracted from sugarcane leaf using alkali extraction according to the response surface methodology. The highest xylan yield (99.42 ± 4.05 % recovery) was obtained using 14.32 % (w/v) NaOH, 13.25:1 liquid: solid ratio, at 121 °C and 15 lb.in2 for 32 min. Sugar composition and FTIR spectrum analyses confirmed its structure as arabinoxylan. The extracted arabinoxylan had a relatively high molecular weight compared to previous studies. Crude endoxylanase from A. pullulans NRRL 58523 was selected for enzymatic hydrolysis of the xylan. The enzyme hydrolyzed well at 50 °C, pH 4.0 and was relatively stable under this condition (87.38 ± 1.26 % of the activity remained after 60 h). XOs, especially xylobiose and xylotriose, were obtained at the maximum yield of 237.51 ± 17.69 mg/g xylan via endoxylanase hydrolysis under the optimum conditions (50 °C, pH 4.0, 65.31 U/g xylan, 53 h). XOs exhibited species-specific prebiotic activity toward three strains of Lactobacillus spp. but not toward Bifidobacterium spp.

IntroductionLinseed or flaxseed (Linum usitassimum L.) contains a prospective source of protein and energy to be utilized in animal feed. This study aimed at re-cycling and value-addition of Linseed Oil Cake (LOC) for formulation of non-conventional carp diets. MethodsThe LOC was bio-processed through solid state fermentation (SSF) with a fish gut bacterium, Bacillus pumilus (KF640221). Nine experimental sets of diets were formulated using raw (R1-R4) and SSF-processed (F1-F4) LOC at 10%, 20%, 30% and 40% levels substituting fishmeal as well as other ingredients in a reference diet, and rohu, Labeo rohita fingerlings (2.08±0.03 g) were fed for 70 days feeding trial. Growth, carcass composition, activities of digestive enzymes, digestibility and haemato-biochemical parameters were studied following standard methodologies.ResultsSSF significantly (P< 0.05) improved crude protein along with amino acids, whereas crude fibre and antinutritional factors were reduced considerably. Experimental diets were isocaloric (4.8 kcal) and isonitrogenous (36%). Diets with bio-processed LOC had significantly better performance than the raw LOC. Fish fed diet F3 with 30% fermented LOC resulted in the highest weight gain (6.25 ± 0.09 g), specific growth rate (% day -1) and carcass protein deposition (16.77±0.34%). Activities of the digestive enzymes (amylase, lipase and protease) were also significantly (P

This study aims to provide a comprehensive understanding of the key factors influencing the rheological behavior and the mechanisms of natural polyelectrolyte complexes (PECs) as flocculation agents for cellulose microfibers (CMFs) and nanofibers (CNFs). PECs were formed by combining two polyelectrolytes: xylan (Xyl) and chitosan (Ch), at different Xyl/Ch mass ratios: 60/40, 70/30, and 80/20. First, Xyl, Ch, and PEC solutions were characterized by measuring viscosity, critical concentration (c*), rheological parameter, ζ-potential, and hydrodynamic size. Then, the flocculation mechanisms of CMF and CNF suspensions with PECs under dynamic conditions were studied by measuring viscosity, while the flocculation under static conditions was examined through gel point measurements, floc average size determination, and ζ-potential analysis. The findings reveal that PEC solutions formed with a lower xylan mass ratio showed higher intrinsic viscosity, higher hydrodynamic size, higher z-potential, and a lower c*. This is due to the high molecular weight, charge, and gel-forming ability. All the analyzed solutions behave as a typical non-Newtonian shear-thinning fluid. The flocculation mechanisms under dynamic conditions showed that a very low dosage of PEC (between 2 and 6 mg PEC/g of fiber) was sufficient to produce flocculation. Under dynamic conditions, an increase in viscosity indicates flocculation at this low PEC dosage. Finally, under static conditions, maximum floc sizes were observed at the same PEC dosage where minimum gel points were reached. Higher PEC doses were required for CNF suspensions than for CMF suspensions. [ABSTRACT FROM AUTHOR]

Mycosporine-like amino acids (MAAs) are natural UV-absorbing compounds found in microalgae and macroalgae. The content of MAAs in algae varies with the seasons and environmental factors. Red alga dulse in Usujiri (Hokkaido, Japan) is an underutilized resource. Therefore, we investigated the amount of MAAs in Usujiri dulse in 2022 to clarify the suitable months for MAA extraction. In addition, we also evaluated the extraction method focusing on the extraction volume. MAAs were prepared via the 20 volumes of 25% ethanol extraction method and detected via HPLC. The results showed that the amount of MAAs on 25 March 2022 showed the highest value (40.4 μmol/g DW) among the samples from 24 January to 13 May. The tendency of suitable samples for MAA preparation corresponded to the term from mid-February to early April, which was the same as the previous three years. Although the surveys from 2019–2021 were performed by using the successive water–methanol method, it was found that the improved method also reflected the monthly variation in MAAs. The extraction of MAAs was performed via 20 or 40 volumes of 25% ethanol at 4 °C for 24 h. The amount of MAAs with 40 volumes of 25% ethanol extraction increased 1.3-fold compared to that with 20 volumes of 25% ethanol extraction. These data are useful information for valuable compound extraction from Usujiri dulse. [ABSTRACT FROM AUTHOR]

Lytic polysaccharide monooxygenases (LPMOs) belonging to the AA14 family are believed to contribute to the enzymatic degradation of lignocellulosic biomass by specifically acting on xylan in recalcitrant cellulose‐xylan complexes. Functional characterization of an AA14 LPMO from Trichoderma reesei, TrAA14A, and a re‐evaluation of the properties of the previously described AA14 from Pycnoporus coccineus, PcoAA14A, showed that these proteins have oxidase and peroxidase activities that are common for LPMOs. However, we were not able to detect activity on cellulose‐associated xylan or any other tested polysaccharide substrate, meaning that the substrate of these enzymes remains unknown. Next to raising questions regarding the true nature of AA14 LPMOs, the present data illustrate possible pitfalls in the functional characterization of these intriguing enzymes. [ABSTRACT FROM AUTHOR]

Studies on the degradation of plant cell wall polysaccharides by fungal extracellular enzymes have attracted recent attention from researchers. Xylan, abundant in hemicellulose, that play great role in connection between cellulose and lignin, has seen interest in its hydrolytic enzymatic complex. In this study, dozens of fungus species spanning genera were isolated from rotting leaves based on their ability to decompose xylan. Among these isolates, a strain with strong xylanase-producing ability was selected for further investigation by genome sequencing. Based on phylogenetic analysis of ITS (rDNA internal transcribed spacer) and LSU (Large subunit 28S rDNA) regions, the isolate was identified as Penicillium oxalicum. Morphological analysis also supported this finding. Xylanase activity of this isolated P. oxalicum 5-18 strain was recorded to be 30.83 U/mL using the 3,5-dinitro-salicylic acid (DNS) method. Further genome sequencing reveals that sequenced reads were assembled into a 30.78 Mb genome containing 10,074 predicted protein-encoding genes. In total, 439 carbohydrate-active enzymes (CAZymes) encoding genes were predicted, many of which were associated with cellulose, hemicellulose, pectin, chitin and starch degradation. Further analysis and comparison showed that the isolate P. oxalicum 5-18 contains a diverse set of CAZyme genes involved in degradation of plant cell wall components, particularly cellulose and hemicellulose. These findings provide us with valuable genetic information about the plant biomass-degrading enzyme system of P. oxalicum, facilitating a further exploration of the repertoire of industrially relevant lignocellulolytic enzymes of P. oxalicum 5-18. [ABSTRACT FROM AUTHOR]

Xylan that comprises roughly 25% of hardwood biomass is undesirable in biorefinery applications involving saccharification and fermentation. Efforts to reduce xylan levels have therefore been made in many species, usually resulting in improved saccharification. However, such modified plants have not yet been tested under field conditions. Here we evaluate the field performance of transgenic hybrid aspen lines with reduced xylan levels and assess their usefulness as short-rotation feedstocks for biorefineries. Three types of transgenic lines were tested in four-year field tests with RNAi constructs targeting either Populus GT43 clades B and C (GT43BC) corresponding to Arabidopsis clades IRX9 and IRX14, respectively, involved in xylan backbone biosynthesis, GATL1.1 corresponding to AtGALT1 involved in xylan reducing end sequence biosynthesis, or ASPR1 encoding an atypical aspartate protease. Their productivity, wood quality traits, and saccharification efficiency were analyzed. The only lines differing significantly from the wild type with respect to growth and biotic stress resistance were the ASPR1 lines, whose stems were roughly 10% shorter and narrower and leaves showed increased arthropod damage. GT43BC lines exhibited no growth advantage in the field despite their superior growth in greenhouse experiments. Wood from the ASPR1 and GT43BC lines had slightly reduced density due to thinner cell walls and, in the case of ASPR1, larger cell diameters. The xylan was less extractable by alkali but more hydrolysable by acid, had increased glucuronosylation, and its content was reduced in all three types of transgenic lines. The hemicellulose size distribution in the GALT1.1 and ASPR1 lines was skewed towards higher molecular mass compared to the wild type. These results provide experimental evidence that GATL1.1 functions in xylan biosynthesis and suggest that ASPR1 may regulate this process. In saccharification without pretreatment, lines of all three constructs provided 8-11% higher average glucose yields than wild-type plants. In saccharification with acid pretreatment, the GT43BC construct provided a 10% yield increase on average. The best transgenic lines of each construct are thus predicted to modestly outperform the wild type in terms of glucose yields per hectare. The field evaluation of transgenic xylan-reduced aspen represents an important step towards more productive feedstocks for biorefineries. [ABSTRACT FROM AUTHOR]

Hemicellulose has potential advantages in food packaging because of its abundant reserves, degradability and regeneration. However, compared with fossil-derived plastic films, hemicellulose-based films show inferior hydrophobicity and barrier properties because of their low degree of polymerization and strong hydrophilicity. Focusing on such issues, this work covers the modification of a xylan/polyvinyl alcohol (PVOH) film using 1,2,3,4-butane tetracarboxylic acid (BTCA) as esterifying agent. The thus prepared composite film was more compact owing to the esterification reaction with xylan and PVOH forming a crosslinked network structure and reducing the distance between molecular chains. The results showed that BTCA had a positive effect on the oxygen barrier, hydrophobicity and mechanical properties of the composite film. The tensile strength of the xylan/PVOH composite film with 10% BTCA content increased from 11.19 MPa to 13.99 MPa. A 20% BTCA loading resulted in an increase in the contact angle of the composite film from 87.1° to 108.2°, and a decrease in the oxygen permeability from 2.11 to 0.43 (cm3·µm)/(m2·d·kPa), corresponding to increase in the contact angle by 24% and a decrease in oxygen permeability by 80%. The overall performance enhancement indicates the potential application of such composites as food packaging. [ABSTRACT FROM AUTHOR]

Abstract Background Glycoside hydrolase (GH) family 30 xylanases are a distinct group of xylanases, most of which have a highly specific catalytic activity for glucuronoxylan. Since GH30 xylanases do not normally carry carbohydrate-binding modules (CBMs), our knowledge of the function of their CBMs is lacking. Results In this work, the CBM functions of CrXyl30 were investigated. CrXyl30 was a GH30 glucuronoxylanase containing tandem CBM13 (CrCBM13) and CBM2 (CrCBM2) at its C terminus, which was identified in a lignocellulolytic bacterial consortium previously. Both CBMs could bind insoluble and soluble xylan, with CrCBM13 having binding specificity for the xylan with l-arabinosyl substitutions, whereas CrCBM2 targeted l-arabinosyl side chains themselves. Such binding abilities of these two CBMs were completely different from other CBMs in their respective families. Phylogenetic analysis also suggested that both CrCBM13 and CrCBM2 belong to novel branches. Inspection of the simulated structure of CrCBM13 identified a pocket that just accommodates the side chain of 3(2)-alpha-l-arabinofuranosyl-xylotriose, which forms hydrogen bonds with three of the five amino acid residues involved in ligand interaction. The truncation of either CrCBM13 or CrCBM2 did not alter the substrate specificity and optimal reaction conditions of CrXyl30, whereas truncation of CrCBM2 decreased the kcat/Km value by 83% (± 0%). Moreover, the absence of CrCBM2 and CrCBM13 resulted in a 5% (± 1%) and a 7% (± 0%) decrease, respectively, in the amount of reducing sugar released by the synergistic hydrolysis of delignified corncob whose hemicellulose is arabinoglucuronoxylan, respectively. In addition, fusion of CrCBM2 with a GH10 xylanase enhanced its catalytic activity against the branched xylan and improved the synergistic hydrolysis efficiency by more than fivefold when delignified corncob was used as substrate. Such a strong stimulation of hydrolysis resulted from the enhancement of hemicellulose hydrolysis on the one hand, and the cellulose hydrolysis is also improved according to the lignocellulose conversion rate measured by HPLC. Conclusions This study identifies the functions of two novel CBMs in CrXyl30 and shows the good potential of such CBMs specific for branched ligands in the development of efficient enzyme preparations.