A recombinant plasmid p beta CBD was constructed for immobilization of Cellulomonas fimi beta-glucosidase (Cbg) using the cellulose-binding domain (CBD) of Bacillus subtilis BSE 616 endo-beta-1,4-glucanase (Beg). The Cbg-CBDBeg fusion protein, 80 kDa, was expressed in Escherichia coli and immobilized to Avicel. Cellobiose was completely hydrolyzed with the immobilized fusion protein. The fusion protein bound to Avicel retained full activity during continuous operation for 24 h at 4 degrees C.