Addition of cloned β-glucosidase enhances the degradation of crystalline cellulose by the Clostridium thermocellum cellulase complex

Abstract

A thermostable β-glucosidase from Clostridium thermocellum which is expressed in Escherichia coli was used to determine the substrate specificity of the enzyme. A restriction map of the β-glucosidase gene cloned in plasmid pALD7 was determined. Addition of the E.coli cell extract (containing the β-glucosidase) to the cellulase complex from C.thermocellum increased the conversion of crystalline cellulose (Avicel) to glucose. The increase was specifically due to hydrolysis of the accumulated cellobiose. A cellulose degradation process using β-glucosidase to assist the potent cellulase complex of C.thermocellum, as shown here can open the way for industrial saccharification of cellulose to glucose.