Heterologous expression, characterization and application of a new β-xylosidase identified in solventogenic Clostridium sp. strain BOH3

Abstract

Abstract A β-xylosidase gene (BxylBOH3) was identified in a solventogenic bacterium Clostridium sp. strain BOH3, which is a member of the glycoside hydrolase family 43 (GH43). The recombinant enzyme of BxylBOH3 was expressed in Escherichia coli with a high specific activity of 48.7 U/mg and a low Km value of 2.71 mM at an optimal temperature of 40 °C and pH of 5.0-6.0, indicating its high affinity for the substrate and enzymatic potency. Moreover, activity of β-xylosidase can be enhanced (>1.6 times) by addition of Zn2+. The concentration of reducing sugar (including xylose and xylooligosaccharides) with the synergism of xylanase and recombinant β-xylosidase was enhanced up to 129.8% (11.93 g/L) after hydrolysis of 30 g/L of xylan for 24 h when comparing with only xylanase (9.19 g/L). Application of this recombinant β-xylosidase together with xylanase improved xylan hydrolysis efficiency, thus leading to increased biofuels productivity from xylan fermented by Clostridium species.