Characterization of a β-Xylosidase from Clostridium clariflavum and Its Application in Xylan Hydrolysis

A beta-xylosidase gene, xyl43C, from Clostridium clariflavum was heterogeneously expressed in Escherichia coli BL21. Xyl43C showed strong activity toward xylobiose, with specific activity of 76.6 U/mg and K-m of 4.97 mM. The optimal pH and temperature of Xyl43C were pH 6.0 and 60 degrees C, respectively. Xyl43C retained 94.4% activity after incubation at 55 degrees C for 1 h, and 75.4% at 60 degrees C for 1 h. It also showed xylose tolerance with IC50 (half maximal inhibitory concentration) of approximately 100 mM. It nearly completely hydrolyzed 2 g/L of xylobiose at enzyme load of 2.51 mg/g xylobiose within 30 min and converted 40 g/L of corncob xylan into xylose at enzyme load of 1.48 mg/g xylan, with a yield of 60.9%. In conclusion, Xyl43C is an efficient xylose-tolerant beta-xylosidase, with promising application potential in saccharification of xylan in biofuels industry.