Two family 11 xylanases from Achaetomium sp. Xz-8 with high catalytic efficiency and application potentials in the brewing industry.

This study identified two family-11 xylanase genes (xynC81 and xynC83) in Achaetomium sp. Xz-8, a thermophilic strain from a desert area with substantial xylanase activity, and successfully expressed them in Pichia pastoris. Their deduced amino acid sequences showed the highest identity of <= 90% to known fungal xylanases and of <= 62% with each other. The purified recombinant xylanases showed optimal activities at pH 5.5 and 60-65 degrees C and exhibited stability over pH 5.0-10.0 and temperatures at 55 degrees C and below. XynC81 had high catalytic efficiency (6082 mL/s/mg), and XynC83 was favorable for xylooligosaccharide production. Under simulated mashing conditions, combination of XynC83 and a commercial beta-glucanase improved the filtration rate by 34.7696, which is much better than that of Novozymes Ultraflo (20.71%). XynC81 and XynC83 had a synergistic effect on viscosity reduction (7.08%), which is comparable with that of Ultraflo (8.47%). Thus, XynC81 and XynC83 represent good candidates for application in the brewing industry.