Biochemical characterization of a novel glycoside hydrolase family 11 xylanase from Chaetomium sp. suitable for bread making

A novel xylanase gene (CsXyn11A) from Chaetomium sp. CQ31 was extracellularly expressed in Aspergillus niger. CsXyn11A belonging to glycoside hydrolase (GH) family 11 shared 72% amino acid identity with the xylanase from Achaetomium sp. Xz-8. High xylanase activity of 3824 U/mL with 10.4 g/L protein concentration was secreted by recombinant A. niger in a 5-L fermentor. CsXyn11A was purified by Q-Sepharose ion-exchange chromatography column. It was optimally active at 70 C and pH 7.0, respectively. The xylanase displayed strict substrate specificity towards different xylans, and showed high activity (1850 U/mg) towards wheat arabinoxylan. This enzyme was further applied in bread making to evaluate its effect on the bread quality. The incorporation of CsXyn11A reduced the development time, stable time and different torque values of dough samples. Addition of CsXyn11A (5 ppm) into the bread making remarkably improved the specific volume by 25.6% and decreased the hardness by 46%. The favorable properties of CsXyn11A suggest that it may be a promise candidate suitable for bread making.