A gene coding for beta-glucosidase from the rumen bacteria, Ruminococc
us albus 7, was cloned into Escherichia call DHS alpha by using plasmi
d pUC19, A R albus 7 genomic library was prepared in E. coli by using
partially Sau3AI-digested DNA. Transformants were screened for beta-gl
ucosidase activity on the basis of formation of blue colonies on LB ag
ar plates containing 5-bromo-4-chloro-3-indolyl-beta-D-glucoside. A cl
one containing beta-glucosidase activity was found and its recombinant
DNA structure was found to contain a 3.1 kilobase insert, beta-Glucos
idase activity against p-nitrophenyl-beta-D-glucoside (PNPG) expressed
by the E. coli clone was found to be 42 times greater than that expre
ssed by the original R albus 7.