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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: A single point mutation in the gene encoding the Xylanase regulator 1 (Xyr1) is responsible for this strong deregulation of endo-xylanase expression and, moreover, a highly elevated basal level of cellulase expression.
Abstract: Trichoderma reesei is an organism involved in degradation of (hemi)cellulosic biomass. Consequently, the corresponding enzymes are commonly used in different types of industries, and recently gained considerable importance for production of second-generation biofuel. Many industrial T. reesei strains currently in use are derived from strain Rut-C30, in which cellulase and hemicellulase expression is released from carbon catabolite repression. Nevertheless, inducing substances are still necessary for a satisfactory amount of protein formation. Here, we report on a T. reesei strain, which exhibits a very high level of xylanase expression regardless if inducing substances (e.g. D-xylose, xylobiose) are used. We found that a single point mutation in the gene encoding the Xylanase regulator 1 (Xyr1) is responsible for this strong deregulation of endo-xylanase expression and, moreover, a highly elevated basal level of cellulase expression. This point mutation is localized in a domain that is common in binuclear zinc cluster transcription factors. Only the use of sophorose as inducer still leads to a slight induction of cellulase expression. Under all tested conditions, the formation of cbh1 and cbh2 transcript level strictly follows the transcript levels of xyr1. The correlation of xyr1 transcript levels and cbh1/cbh2 transcript levels and also their inducibility via sophorose is not restricted to this strain, but occurs in all ancestor strains up to the wild-type QM6a. Engineering a key transcription factor of a target regulon seems to be a promising strategy in order to increase enzymes yields independent of the used substrate or inducer. The regulatory domain where the described mutation is located is certainly an interesting research target for all organisms that also depend so far on certain inducing conditions.
111 citations
TL;DR: Two extracellular xylanase produced by the thermotolerant fungus Aspergillus caespitosus grown in sugar cane bagasse were purified and characterized and the action of both xylanases mainly that of xyl II, on kraft pulp reduced kappa number and increased pulp viscosity.
110 citations
TL;DR: It is suggested that the ligninolytic-enzyme-encoding genes that are expressed during solid substrate degradation differ from those expressed in liquid culture or are allelic variants of their liquid culture counterparts.
Abstract: The specific enzymes associated with lignin degradation in solid lignocellulosic substrates have not been identified. Therefore, we examined extracts of cultures of Phanerochaete chrysosporium that were degrading a mechanical pulp of aspen wood. Western blot (immunoblot) analyses of the partially purified protein revealed lignin peroxidase, manganese-dependent peroxidase (MnP), and glyoxal oxidase. The dominant peroxidase, an isoenzyme of MnP (pI 4.9), was isolated, and its N-terminal amino acid sequence and amino acid composition were determined. The results reveal both similarities to and differences from the deduced amino acid sequences from cDNA clones of dominant MnP isoenzymes from liquid cultures. Our results suggest, therefore, that the ligninolytic-enzyme-encoding genes that are expressed during solid substrate degradation differ from those expressed in liquid culture or are allelic variants of their liquid culture counterparts. In addition to lignin peroxidase, MnP, and glyoxal oxidase, xylanase and protease activities were present in the extracts of the degrading pulp.
110 citations
TL;DR: The purification and characterization of xylanase from Aspergillus ficuum AF-98 were investigated and it was found that the enzyme exhibited K(m) and V(max) values of 3.267 mg/mL, 18.38 M/min/mg for beechwood xylan and 3.1M/min-mg for birchwoodxylan, respectively.
110 citations
TL;DR: The stability of the enzyme was found to be significantly greater than those of the cellulases and xylanases produced by other streptomycetes.
Abstract: The production of cellulases and of xylanase by Streptomyces lividans 1326 was studied under different growth conditions. The strain grew between 18°C and 46°C and is therefore thermotolerant. Submerged cultures of the microorganism, when grown on a defined salt medium containing xylan as main carbon source, exhibited an overall cellulolytic activity as determined by the filter paper test. S. lividans produced optimal levels of extracellular β-1,4-glucan-glucanohydrolase (1 IU/ml) and large amounts of β-1,4-xylanxylanohydrolase (50 IU/ml) at 40°C. A better production of both enzymes was observed when xylan instead of cellulose was used as substrate. The stability of the enzyme was found to be significantly greater than those of the cellulases and xylanases produced by other streptomycetes. The optimal incubation temperatures for the enzyme assays were 55°C and 60°C for CM-cellulase and xylanase respectively and optimal pH values were found in the range of pH 6–7.
109 citations