Polyacrylamides as immobilization supports for use of hydrolytic enzymes in organic media

Polyacrylamide beads and celite were used for immobilization of bovine α-chymotrypsin and lipase B from Candida antarctica. Polyacrylamides with a high degree of cross-linking afforded high catalytic rates when used as immobilization matrices. Derivatization of the polymer with carboxyl and tertiary amino groups prior to immobilization caused no significant changes in α-chymotrypsin behavior. The water absorption isotherms for the different supports revealed that the higher the degree of cross-linking the higher the water content of the support is. Leveling off of the enzyme activity above a certain enzyme loading of the supports indicated mass transfer limitations. Diffusional limitations were less pronounced for the polymers with a high degree of cross-linking. This phenomenon may be attributed to their larger surface area. Diffusional limitations were obvious when celite and the polyacrylamides with a low degree of cross-linking were employed. Acetone precipitation of the enzyme was more favorable for enzyme activity than vacuum drying, particularly when the polyacrylamide was employed as the support. The acetone treatment resulted in a morphologically different surface structure of the polymer, as compared to the structure observed after vacuum drying.