Cloning, expression and characterization of a novel acidic xylanase, XYL11B, from the acidophilic fungus Bispora sp MEY-1

A xylanase gene (xyl11B) was cloned from Bispora sp. MEY-1 and expressed in Pichia pastons. xyl11B, with a 66-bp intron, encodes a mature protein of 219 residues with highest identity (57.1%) to the Trichoderma reesei xylanase of glycoside hydrolase family 11. The purified recombinant XYL11B was acidophilic, exhibiting maximum activity at pH 2.6 and 65 degrees C. The enzyme was also thermostable, pH stable, and was highly resistant to both pepsin and trypsin, suggesting good performance in the digestive tract as a feed supplement to improve animal nutrition. The activity of XYL11B was enhanced by most metal ions but was inhibited weakly by Hg2+. Pb2+ and Cu2+. which strongly inhibit many other xylanases. The specific activity of XYL11B for oat spelt xylan substrate was 2049 U mg(-1). The main hydrolysis products of xylan were xylose and xylobiose. (C) 2009 Elsevier Inc. All rights reserved.