Xylanase

About: Xylanase is a research topic. Over the lifetime, 7099 publications have been published within this topic receiving 163793 citations.

A third xylanase from Trichoderma reesei PC-3-7

Abstract: A third xylanase (Xyn III) from Trichoderma reesei PC-3–7 was purified to electrophoretic homogeneity by gel filtration and ion-exchange chromatographies. The enzyme had a molecular mass of 32 kDa, and its isoelectric point was 9.1. The pH optimum of Xyn III was 6.0, similar to that of Xyn II, another basic xylanase of T. reesei. The purified Xyn III showed high activity with birchwood xylan but no activity with cellulose and aryl glycoside. The hydrolysis of birchwood xylan by Xyn III produced mainly xylobiose, xylotriose and other xylooligosaccharides. The amino acid sequences of the N-terminus and internal peptides of Xyn III exhibited high homology with the family F xylanases, showing that they were distinct from those of Xyn I and Xyn II of T. reesei, which belong to family G. These results reveal that Xyn III is a new specific endoxylanase, differing from Xyn I and Xyn II in T. reesei. It is noteworthy that this novel xylanase was induced only by cellulosic substrates and l-sorbose but not by xylan and its derivarives. Furthermore, T. reesei PC-3-7 produced Xyn III in quantity when grown on Avicel or lactose as a carbon source, while T. reesei QM9414 produced little or no Xyn III.

Production, isolation and partial purification of xylanases from an Aspergillus sp

Abstract: AnAspergillus sp., isolated from a rubbish dump, produced 10.6 IU ml-1 xylanase activity. Two xylanases were recognized and each was purified to homogeneity by two-stage chromatography on DEAE-and CM-Sepharose. Xylanase I had a pI of 7.2 and anM r of 26 kDa whereas xylanase II had a pI of 4.7 and anM r of 21 kDa. At 50°C, xylanase I was stable for 2.5 h but xylanase II was only stable for 1 h.

Characterization of Unbleached Kraft Pulps by Enzymatic Treatment, Potentiometric Titration and Polyelectrolyte Adsorption

Abstract: The surface properties of unbleached softwood (Pinus sylvestris) and hardwood (Betula verrucosa) kraft pulps were modified by treating the fibre surfaces with specific xylanase and mannanase (Trichoderma reesei). The amounts and accessibilities of surface carboxyl groups in untreated and enzyme-treated fibres were analyzed using adsorption of cationic polyelectrolytes and high precision potentiometric titration. According to the potentiometric titration both softwood and hardwood pulps contained two types of acidic groups, one with pK 1 ≃ 3.3 (uronic acid in xylan) and one with pK 2 ≃ 5.5 (probably carboxylic group in lignin). The relative amount of the weaker acid in softwood and hardwood pulp was 10% and 20% of the total acid content, respectively. The ratio of the two acids in pulps was not changed by mannanase treatment, while xylanase treatment decreased the relative amount of the stronger acid. This indicates that the major part of the carboxylic groups are bound to xylan. Xylanase treatment removed about 30% of the xylan in both birch and pine pulps and, consequently, 22% of the acid groups in hardwood pulp but only 8% of the acid groups in softwood pulp. Hence, in softwood kraft pulp fibres the content of uronic acid side-groups in accessible xylan on the surfaces of the fibres is lower than that on the hardwood fibres.

Xylanase and acetyl xylan esterase activities of XynA, a key subunit of the Clostridium cellulovorans cellulosome for xylan degradation.

Abstract: The Clostridium cellulovorans xynA gene encodes the cellulosomal endo-1,4-β-xylanase XynA, which consists of a family 11 glycoside hydrolase catalytic domain (CD), a dockerin domain, and a NodB domain. The recombinant acetyl xylan esterase (rNodB) encoded by the NodB domain exhibited broad substrate specificity and released acetate not only from acetylated xylan but also from other acetylated substrates. rNodB acted synergistically with the xylanase CD of XynA for hydrolysis of acetylated xylan. Immunological analyses revealed that XynA corresponds to a major xylanase in the cellulosomal fraction. These results indicate that XynA is a key enzymatic subunit for xylan degradation in C. cellulovorans.