The use of glutaraldehyde-modified β-glucosidase entrapped within structurally stable PGAG gel spheres for the continuous hydrolysis of cellobiose has been demonstrated. Such spheres may be useful in a bioprocess concerned with the enzymatic conversion of cellulosic materials to fuels and chemicals. It will be important, however, to maintain higher loadings of cellobiase activity within the spheres than those achieved in the present study. This will be possible through the formation of stable covalent bonds between β-glucosidase molecules prior to their entrapment. Finally, if the modification is carried out in the presence of cellobiose, it appears as if there is virtually no loss in catalytic activity. © 1992 Humana Press Inc.