Preparation of immobilized enzymes by N‐Vinylpyrrolidone and the general properties of the glucoamylase gel

Immobilized glucoamylase, invertase, and β‐galactosidase were prepared by using N‐vinylpyrrolidone monomer (VP) under γ‐ray irradiation. The enzyme‐VP solutions were gelled by irradiation with 2.9 Mrad and the added enzymes were almost completely entrapped. Activity losses on entrapping were 55% for the VP‐glucoamylase gel, and more than 90% in the case of VP‐invertase and VP‐β‐galactosidase gels. No leakage of enzyme from these gels could be detected within 1 hr. The VP‐glucoamylase gel was capable of hydrolyzing dextrin (mol wt 10,400) to glucose and the glucose equivalent was equal to that obtain able with native enzyme. The optimum temperature, heat stability, pH activity curve, and pH stability of VP‐glucoamylase gel were slightly inferior to those of native enzyme, while Km was a little larger than that of native enzyme.