A thermostable Gloeophyllum trabeum xylanase with potential for the brewing industry

A xylanase gene of glycoside hydrolase family 10, GtXyn10, was cloned from Gloeophyllum trabeum CBS 900.73 and expressed in Pichia pastoris GS115. Purified recombinant GtXyn10 exhibited significant activities to xylan (100.0%), lichenan (11.2%), glucan (15.2%) and p-nitrophenol-β-cellobiose (18.6%), demonstrated the maximum xylanase and glucanase activities at pH 4.5-5.0 and 75 °C, retained stability over the pH range of 2.0-7.5 and at 70 °C, and was resistant to pepsin and trypsin, most metal ions and SDS. Multiple sequence alignment and modeled-structure analysis identified a unique Gly48 in GtXyn10, and site-directed mutagenesis of Gly48 to Lys improved the temperature optimum up to 80 °C. Under simulated mashing conditions, GtXyn10 (80 U) reduced the mash viscosity by 12.8% and improved the filtration rate by 31.3%. All these properties above make GtXyn10 attractive for potential applications in the feed and brewing industries.