Characterization of a novel xylanase from an extreme temperature hot spring metagenome for xylooligosaccharide production.

In this study, the metagenomic resource generated from an aquatic habitat of extreme temperature was screened for the identification of a novel xylanase, XynM1. Gene sequence analysis designated it as a member of glycoside hydrolase (GH) family 10. The metagenomic DNA fragment was cloned, expressed in Escherichia coli, and the purified protein was biochemically characterized. The optimum temperature and pH for the XynM1 xylanase were found to be at 80 °C and 7, respectively. It exhibited worthwhile pH stability by retaining about 70% activity in the range of pH 6 to 9 after the exposure for 12 h at 25 °C. Thermostability analysis established considerable heat tolerance in XynM1 protein at elevated temperatures, displaying about 50% residual activity after the exposure of 40 °C, 50 °C, 60 °C, and 70 °C for 20 h, 12 h, 6 h, and 1.5 h, respectively. The effects of additives such as metals, surfactants, and organic solvents were evaluated on the activity of XynM1. It was able to retain about 50% of its initial activity in the presence of NaCl concentration of 1 to 5 M. The novel xylanase was capable of hydrolyzing the hemicellulosic polymer, derived from diverse biomass sources, e.g., beechwood xylan, wheat arabinoxylan, corncob xylan, and sweet sorghum xylan. The XynM1-treated beechwood xylan manifested catalytic release of xylooligosaccharides (XOS) of 2-6 DP. The novel GH10 xylanase is a promising biocatalyst that could be ascribed for biomass conversion and production of prebiotic XOS biomolecules.