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Xylanase
About: Xylanase is a research topic. Over the lifetime, 7099 publications have been published within this topic receiving 163793 citations.
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TL;DR: Optimisation of enzymatic hydrolyses allowed the use of lower quantities of enzymes and improved the cost effectiveness of the process.
301 citations
TL;DR: The ability of T. lanuginosus to produce high levels of cellulase-free thermostable xylanase has made the fungus an attractive source of thermostably xylan enzyme with potential as a bleach-boosting agent in the pulp and paper industry and as an additive in the baking industry.
Abstract: The non-cellulolytic Thermomyces lanuginosus is a widespread and frequently isolated thermophilic fungus. Several strains of this fungus have been reported to produce high levels of cellulase-free β-xylanase both in shake-flask and bioreactor cultivations but intraspecies variability in terms of β-xylanase production is apparent. Furthermore all strains produce low extracellular levels of other hemicellulases involved in hemicellulose hydrolysis. Crude and purified hemicellulases from this fungus are stable at high temperatures in the range of 50–80°C and over a broad pH range (3–12). Various strains are reported to produce a single xylanase with molecular masses varying between 23 and 29 kDa and pI values between 3.7 and 4.1. The gene encoding the T. lanuginosus xylanase has been cloned and sequenced and is shown to be a member of family 11 glycosyl hydrolases. The crystal structure of the xylanase indicates that the enzyme consists of two β-sheets and one α-helix and forms a rigid complex with the three central sugars of xyloheptaose whereas the peripheral sugars might assume different configurations thereby allowing branched xylan chains to be accepted. The presence of an extra disulfide bridge between the β-strand and the α-helix, as well as to an increase in the density of charged residues throughout the xylanase might contribute to the thermostability. The ability of T. lanuginosus to produce high levels of cellulase-free thermostable xylanase has made the fungus an attractive source of thermostable xylanase with potential as a bleach-boosting agent in the pulp and paper industry and as an additive in the baking industry.
298 citations
TL;DR: In this article, the authors found that glucose release increased nearly linearly with residual xylose removal by enzymes for all pretreatments despite substantial differences in their relative yields, and a mechanism was suggested to explain the incremental increase in glucose release with xylanase supplementation.
288 citations
TL;DR: In this article, the authors measured polysaccharide-degrading activity in different fractions of human faeces and found that bacterial poly-saccharidases and glycosidases were primarily associated with the washed bacterial fractions.
Abstract: Measurements of polysaccharide-degrading activity in different fractions of human faeces showed that bacterial polysaccharidases and glycosidases were primarily associated with the washed bacterial fractions. Amylase, pectinase and xylanase were the major polysaccharide-hydrolysing enzymes detected, whilst α-L-arabinofuranosidase, β-D-xylosidase, β-D-galactosidase and β-D-glucosidase were the most active glycosidases. Starch and 3 non-starch polysaccharides (NSP; pectin, xylan and arabinogalactan) were fermented by mixed populations of human faecal bacteria in batch culture. Detailed carbohydrate analysis demonstrated that starch and pectin were the most rapidly degraded substrates and that arabinogalactan and the relatively insoluble polysaccharide xylan were broken down more slowly. Free sugars and oligosaccharides did not accumulate in culture media with any polysaccharide tested. Time-course measurements of polysaccharide remaining in the batch culture fermentations showed that the arabinose side chains of pectin, xylan and arabinogalactan were co-utilised with the backbone sugars. In these cultures, polysaccharide-degrading activity was mainly cell-associated, but extracellular polysaccharidase activity increased as the fermentations progressed. Molar ratios of acetate, propionate and butyrate produced in these experiments were dependent upon the polysaccharide substrate tested. Molar ratios of acetate, propionate and butyrate in the starch, arabinogalactan, xylan and pectin fermentations were 50:22:29, 50:42:8, 82:15:3, and 84:14:2, respectively. The presence of starch did not inhibit the breakdown of arabinogalactan, xylan or pectin by faecal bacterial, providing evidence that multicomponent substrate utilisation occurs when complex populations of faecal bacteria are provided with mixed polysaccharide substrates.
273 citations
TL;DR: The two main xylanases produced by Trichoderma reesei were purified to electrophoretic homogeneity by ion-exchange and gel chromatography and clearly preferred polymeric substrates to xylo-oligosaccharides.
271 citations