Characterization of a neutral recombinant xylanase from Thermoactinospora rubra YIM 77501(T).

A xylanase gene (TrXyn10) from Thermoactinospora rubra YIM 77501(T) was cloned and expressed in Escherichia coli. The amino acid sequence displayed 78% homology with Microbispora mesophila xylanase (WP_062413927.1). The recombinant xylanase (TrXyn10), with MW 46.1 kDa, could hydrolyse beechwood, birchwood and oatspelt xylan. Based on the sequence, enzymatic properties and tertiary structure of the protein, TrXyn10 belongs to glycoside hydrolase family 10 (GH10). The optimal pH and temperature for the recombinant enzyme were determined to be 7.0 and 55 °C, respectively. TrXyn10 was stable over a wide pH range, and it retained more than 45% of the total activity at pH 6.0-12.0 for 12 h. In addition, the activity was greatly promoted, by approximately 200% of the initial activity, after incubation at pH 6.0 and 7.0 for 12 h. Based on enzymatic properties and product analysis, we showed that TrXyn10 is a neutral endoxylanase.