Immobilization of β-Galactosidase on an Insoluble Carrier with a Polyisocyanate Polymer. I. Preparation and Properties

Abstract

Active β-galactosidase was immobilized on a polyisocyanate polymer previously applied to Teflon stirring bars. Maximum enzyme activity was attained by immobilizing the enzyme in phosphate buffer at pH 5.0. Although more β-galactosidase was immobilized at lower pH values, percentage of soluble specific activity remained nearly constant (about 19%) at pH values ranging from 5.0 to 8.5. The immobilized enzyme was stable for prolonged periods, and soluble enzymic activity was absent. Manganese or magnesium ions activated both soluble and immobilized β-galactosidase, but the percent activation was less for the immobilized enzyme, possibly due to hindered conformational changes. Immobilized β-galactosidase was active at pH 8.75 and possessed good stability at this pH as indicated by subsequent assay at pH 6.5. The immobilized β-galactosidase was used continuously up to 137.6 h with less sensitivity to glucose inhibition compared to the soluble enzyme. © 1973, American Dairy Science Association. All rights reserved.