A xylanase with broad pH and temperature adaptability from Streptomyces megasporus DSM 41476, and its potential application in brewing industry

A xylanase gene, xynAM6, was isolated from the genomic DNA library of Streptomyces megasporus DSM 41476 using colony PCR screening method. The 1440-bp full-length gene encodes a 479-amino acid peptide consisting of a putative signal peptide of 36 residues, a family 10 glycoside hydrolase domain and a family 2 carbohydrate-binding module. The mature peptide of xynAM6 was successfully expressed in Pichia pastoris GS115. The optimal pH and temperature were pH 5.5 and 70 °C, respectively. The enzyme showed broad temperature adaptability (>60% of the maximum activity at 50-80 °C), had good thermostability at 60 °C and 70 °C, remained stable at pH 4.0-11.0, and was resistant to most proteases. The Km and Vmax values for oat spelt xylan were 1.68 mg ml−1 and 436.76 μmol min−1 mg−1, respectively, and 2.33 mg ml−1 and 406.93 μmol min−1 mg−1 for birchwood xylan, respectively. The hydrolysis products of XYNAM6 were mainly xylose and xylobiose. Addition of XYNAM6 (80 U) to the brewery mash significantly reduced the filtration rate and viscosity by 36.33% and 35.51%, respectively. These favorable properties probably make XYNAM6 a good candidate for application in brewing industry.