Molecular Cloning of Ruminococcus albus Cellulase Gene

The gene directing the synthesis of the β-1,4-endoglucanase (1,4-d-glucan glucohydrase) (EC 3.2.1.4) of Ruminococcus albus F-40 was cloned in Escherichia coli C600. The recombinant plasmid pRA1 contained a 3.6 kilobase pair(kb)-Hind III fragment derived from R. albus. Forty-five percent of the cellulase activity encoded by pRA 1 was detected in the periplasmic space and the remaining 55% was in the inner cellular fraction. The optimum pH and temperature of the cloned enzyme were pH 5.7 and 37°C, respectively. The enzyme could digest carboxymethyl cellulose (CMC) and lichenan, but it was inactive for laminarin, xylan, and cellobiose.