Thermophilic xylanases are of great interest for their wide industrial application prospects. Here we identified a thermophilic xylanase (XynC01) of glycoside hydrolase (GH) family 10 in a thermophilic fungal strain Achaetomium sp. Xz-8. The deduced amino acids of XynC01 showed the highest identity of <= 52% to experimentally verified xylanases. XynC01 was functionally expressed in Pichia pastoris, showed optimal activity at pH 5.5 and 75 C with stability over a broad pH range (pH 4.0-10.0) and at temperatures of 55 C and below. XynC01 had the highest catalytic efficiency (k(cat)/K-m 3710 mL/s/mg) ever reported for all GH 10 xylanases, and was resistant to all tested metal ions and chemical reagents. Its hydrolysis products of various xylans were simple, mainly consisting of xylobiose and xylose. Under simulated mashing conditions, XynC01 alone had a comparable effect on filtration improvement with Ultraflo from Novozymes (20.24% vs. 20.71%), and showed better performance when combined with a commercial beta-glucanase (38.50%). Combining all excellent properties described above, XynC01 may find diverse applications in industrial fields, especially in the brewing industry. (C) 2013 Elsevier Ltd. All rights reserved.