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Sugarcane (Saccharum spp.) is a genetically complex crop with great potential for the second-generation (2 G) ethanol industry. Despite this, there is scarce knowledge of the variability of bagasse cell-wall components and its association with agronomic traits that could be used in the selection of cultivars with improved bagasse digestibility. In this work, the acid detergent fiber method was used to determine cellulose, hemicellulose, and acid detergent lignin (ADL) in a sugarcane progeny from crossing two commercial cultivars, and in two energy-cane biotypes. Additionally, acetyl bromide-soluble lignin was determined and compared with ADL values. Despite the crossed parents showing similar bagasse composition, transgressive inheritance observed in the progeny for all bagasse cell-wall components underlines the possibility of improving sugarcane for specific bioenergetic uses. Additionally, the low association between cell-wall and yield components found in this work, suggests that indirect selection of cell-wall components for 2 G ethanol industry through agronomic traits would have a limited impact on improving the biomass composition. [ABSTRACT FROM AUTHOR]

SUMMARY: Cell walls are dynamic and multi‐component materials that play important roles in many areas of plant biology. The composition and interactions of the structural elements give rise to material properties, which are modulated by the activity of wall‐related enzymes. Studies of the genes and enzymes that determine wall composition and function have made great progress, but rarely take account of potential compensatory changes in wall polymers that may accompany and accommodate changes in other components, particularly for specific polysaccharides. Here, we present a method that allows the simultaneous examination of the mass distributions and quantities of specific cell wall matrix components, allowing insight into direct and indirect consequences of cell wall manipulations. The method employs gel‐permeation chromatography fractionation of cell wall polymers followed by enzyme‐linked immunosorbent assay to identify polymer types. We demonstrate the potential of this method using glycan‐directed monoclonal antibodies to detect epitopes representing xyloglucans, heteromannans, glucuronoxylans, homogalacturonans (HGs) and methyl‐esterified HGs. The method was used to explore compositional diversity in different Arabidopsis organs and to examine the impacts of changing wall composition in a number of previously characterized cell wall mutants. As demonstrated in this article, this methodology allows a much deeper understanding of wall composition, its dynamism and plasticity to be obtained, furthering our knowledge of cell wall biology. [ABSTRACT FROM AUTHOR]

Biotechnologies that aim to produce renewable fuels, chemicals, and bioproducts from residual ligno(hemi)cellulosic biomass mostly rely on enzymatic depolymerization of plant cell walls (PCW). This process requires an arsenal of diverse enzymes, including xylanases, which synergistically act on the hemicellulose, reducing the long and complex xylan chains to oligomers and simple sugars. Thus, xylanases play a crucial role in PCW depolymerization. Until recently, the largest xylanase family, glycoside hydrolase family 11 (GH11) has been exclusively represented by endo-catalytic β-1,4- and β-1,3-xylanases. Analysis of a metatranscriptome library from a microbial lignocellulose community resulted in the identification of an unusual exo-acting GH11 β-1,4-xylanase (MetXyn11). Detailed characterization has been performed on recombinant MetXyn11 including determination of its low-resolution small-angle X-ray scattering (SAXS) molecular envelope in solution. Our results reveal that MetXyn11 is a monomeric globular enzyme that liberates xylobiose from heteroxylans as the only product. MetXyn11 has an optimal activity in a pH range from 6 to 9 and an optimal temperature of 50 °C. The enzyme maintained above 65% of its original activity in the pH range 5 to 6 after being incubated for 72 h at 50 °C. Addition of the enzyme to a commercial enzymatic cocktail (CelicCtec3) promoted a significant increase of enzymatic hydrolysis yields of hydrothermally pretreated sugarcane bagasse (16% after 24 h of hydrolysis). [ABSTRACT FROM AUTHOR]

The aim of producing sustainable liquid biofuels and chemicals from lignocellulosic biomass remains high on the sustainability agenda, but is challenged by the costs of producing fermentable sugars from these materials. Sugars from plant biomass can be fermented to alcohols or even alkanes, creating a liquid fuel in which carbon released on combustion is balanced by its photosynthetic capture. Large amounts of sugar are present in the woody, nonfood parts of crops and could be used for fuel production without compromising global food security. However, the sugar in woody biomass is locked up in the complex and recalcitrant lignocellulosic plant cell wall, making it difficult and expensive to extract. In this paper,wereview what is known about the major polymeric components of woody plant biomass, with an emphasis on the molecular interactions that contribute to its recalcitrance to enzymatic digestion. In addition, we review the extensive research that has been carried out in order to understand and reduce lignocellulose recalcitrance and enable more cost-effective production of fuel from woody plant biomass. [ABSTRACT FROM AUTHOR]

Background: Miscanthus is a major bioenergy crop in Europe and a potential feedstock for second generation biofuels. The most efficient and realistic method to produce fermentable sugars from lignocellulosic biomass is by enzymatic hydrolysis, assisted by thermo-chemical pretreatment. Recently, microwave technology has drawn growing attention, because of its unique effects and performance on biomass. Result: In this work, microwave energy was applied to facilitate NaOH and H2SO4 pretreatment for Miscanthus under different temperatures (130-200 °C) for 20 min. The yields of reducing sugars from Miscanthus during the pretreatment process increased up to 180 °C and then declined with increasing temperature. Out results here showed a remarkable sugar yield from available carbohydrate (73 %) at the temperature of 180 °C by using 0.2 M H2SO4. In comparison with conventional heating pretreatment studied at same temperature with same biomass material, the reducing sugar release in this study was 17 times higher within half the time. It was highlighted that the major sugar component could be tuned by changing pretreatment temperature or pretreatment media. Optimally, the glucose and xylose yield from available carbohydrate are 47 and 22 % by using 0.2 M H2SO4 and NaOH respectively when temperature was 180 °C. The digestibility of pretreated Miscanthus was 10 times higher than that of untreated biomass. 68-86 % of the lignin content was removed from biomass by 0.2 M NaOH. Simultaneous saccharification fermentation (SSF) results showed an ethanol production of 143-152 mg/g biomass by using H2SO4/NaOH microwave assisted pretreatment, which is 7 times higher than that of untreated Miscanthus. Biomass morphology was studied by SEM, showing temperature has a strong influence on lignin removal process, as different lignin deposits were observed. At the temperature of 180 °C, NaOH pretreated biomass presented highly exposed fibres, which is a very important biomass characteristic for improved enzymatic hydrolysis. Conclusion: Compared to conventional pretreatment, microwave assisted pretreatment is more energy efficient and faster, due to its unique heating mechanism leading to direct interaction between the polar part of biomass and electromagnetic field. The results of this work present promising potential for using microwave to assist biomass thermo-chemical pretreatment. [ABSTRACT FROM AUTHOR]

Background: Efficient deconstruction of lignocellulosic biomass into simple sugars in an economically viable manner is a prerequisite for its global acceptance as a feedstock in bioethanol production. This is achieved in nature by suites of enzymes with the capability of efficiently depolymerizing all the components of lignocellulose. Here, we provide detailed insight into the repertoire of enzymes produced by microorganisms enriched from the gut of the crop pathogen rice yellow stem borer (Scirpophaga incertulas). Results: A microbial community was enriched from the gut of the rice yellow stem borer for enhanced rice straw degradation by sub-culturing every 10 days, for 1 year, in minimal medium with rice straw as the main carbon source. The enriched culture demonstrated high cellulolytic and xylanolytic activity in the culture supernatant. Metatranscriptomic and metaexoproteomic analysis revealed a large array of enzymes potentially involved in rice straw deconstruction. The consortium was found to encode genes ascribed to all five classes of carbohydrate-active enzymes (GHs, GTs, CEs, PLs, and AAs), including carbohydrate-binding modules (CBMs), categorized in the carbohydrate-active enzymes (CAZy) database. The GHs were the most abundant class of CAZymes. Predicted enzymes from these CAZy classes have the potential to digest each cell-wall components of rice straw, i.e., cellulose, hemicellulose, pectin, callose, and lignin. Several identified CAZy proteins appeared novel, having an unknown or hypothetical catalytic counterpart with a known class of CBM. To validate the findings, one of the identified enzymes that belong to the GH10 family was functionally characterized. The enzyme expressed in E. coli efficiently hydrolyzed beechwood xylan, and pretreated and untreated rice straw. Conclusions: This is the first report describing the enrichment of lignocellulose degrading bacteria from the gut of the rice yellow stem borer to deconstruct rice straw, identifying a plethora of enzymes secreted by the microbial community when growing on rice straw as a carbon source. These enzymes could be important candidates for biorefineries to overcome the current bottlenecks in biomass processing. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2 sequential approaches of experimental design were used to evaluate 5 variables. • Optimized conditions have a sugar release 8 times higher than rice husks in natura. • Silica of 97 % purity can be isolated from the alkaline liquor at high yields. • Lignin and hemicellulose were removed from rice husks in the acid pretreatment step. • Surprisingly, the alkali step removed mainly silica (not lignin) from the substrate. In this work, a two-step pretreatment using acid and alkali was optimized for rice rusks (Oryza sativa) using a 25−1 fractional factorial design (FFD), followed by a central composite design (CCD) to further optimization of enzymatic saccharification. The effect of five variables was simultaneously evaluated: H 2 SO 4 concentration (from 0–5.4 % w/w); NaOH concentration (0–6 % w/w); temperature (85–125 °C); time (20–100 min) and solid to liquid ratio (S/L = 5–12.5 % w/w). The best pretreatment conditions were: 1.8 % w/w of H 2 SO 4 in the first step and 6 % w/w of NaOH at 85 °C for 100 min at a S/L = 12.5 % (w/w) in the alkaline step, which resulted in 58.7 mg of glucose/g substrate, an 8-fold increase compared to the sample in natura (7 mg/g). In rice husks, in contrast to the results commonly found in literature, NaOH extracts mainly silica instead of lignin, while H 2 SO 4 has an important role in lignin removal. High purity silica (97 %) was isolated at high yields (70 %) from the alkaline liquor by a simple and scalable process, which could contribute to making ethanol production from this biomass economically viable. [ABSTRACT FROM AUTHOR]

• Microwave thermochemical pretreatments efficiently decomposed hemicellulose. • Microwave thermochemical pretreatments produced high yields of monosaccharides. • Microwave thermochemical pretreatments removed 96.1 % lignin content from biomass. • Efficient microwave thermochemical pretreatment was completed within 5 min. • Microwave heating consumed 25–34 folds less energy than conventional heating. Microwave (MW) heating is attracting great attention in biorefinery processes, because of its special dipole rotation heating mechanism. In the current study, MW and conventional heating methods were employed to assist the thermochemical pretreatments (H 2 O, H 2 SO 4 or NaOH) of maize stem biomass. Their influences on sugar release and biomass compositions during pretreatments were comparably evaluated. Compared to conventional heating pretreatment, MW thermochemical pretreatments are highly efficient in sugar recovery, contributing to 4.3 times higher amount of sugar release (1.25 vs 0.30 μmol/mg biomass) with reaction time 8 times shorter (5 vs 40 min) and selectively producing glucose as the major constituent (0.75 μmol/mg biomass) using 0.2 M H 2 SO 4 as pretreatment media. MW thermochemical pretreatment also effectively removed lignin (up to 91.6 %) within 5 min, which was significantly higher than conventional heating pretreatment (51.2 %). Conventional heating pretreatment successfully removed hemicellulose and converted the crystalline cellulose into amorphous cellulose, which is probably due to its longer heating time. Rapid MW thermochemical pretreatments efficiently fractionated hemicellulose and removed lignin content while keeping the crystalline cellulose structure. MW and conventional heating pretreatments led to similar digestibility of biomass solid residues. Overall, MW thermochemical pretreatment represents an energy efficient alternative strategy, as it consumed 25–34 folds less energy than conventional heating pretreatment for effective biomass fractionation and value-added chemical production. [ABSTRACT FROM AUTHOR]