Entrapping of acid phosphatase in poly(2‐hydroxyethyl methacrylate) matrices: Preparation and kinetic properties

Abstract

Abstract The present work was undertaken to determine the influence of immobilization of acid phosphatase by entrapment in poly(2‐hydroxyethyl methacrylate) (poly‐HEMA) gels on the rate and duration of p ‐nitrophenyl phosphate hydrolysis. This enzyme was selected as model system for the sake of comparison with other immobilization techniques studied previously making use of natural polymers. Under certain conditions, catalyst inactivation induced by chemical agents employed during polymerization was very low. Activity recovery in the enzymatically filled hydrogels depends on acid phosphatase loading and attains a maximum at 2 mg per gram of support. The use of low molecular weight linear polymers as matrix fillers is advisable. The best results were achieved with poly(ethylene oxide) PEG 1500, but PEG 6000 and poly( N ‐vinylpyrrolidone) PVP 10 000 are also effective. Bovine serum albumin (BSA) is useless. The highest value of activity recovery obtained was 24% that of free enzyme. Roughly 30% of enzyme is retained in active form in the hydrogel and works with an efficiency ranging from 97% to 90% depending on average particle size. The kinetic parameters K m and E a suggest the presence of a combined diffusive and enzymatic reaction‐controlling mechanism. Only a minor shift of optimum pH was observed. Both operational and storage stability are largely improved upon entrapping in hydrogels.