Abstract: Oxirane groups can react with the amino groups of enzyme under mild conditions so that the enzyme molecules are immobilized on the copolymer support containing oxirane. A series of macroporous hydrophilic copolymers(GNM) containing oxirane were synthesized by inverse suspension polymerization with glycidyl methacrylate(GMA) as the reactive monomer, N-vinyl-2-pyrrolidone(NVP) as the hydrophilic comonomer, N,N′-methylene-bis-acrylamide(MBAA) as the crosslinking agent, and methanol and water as the porogenic agent and used as the support for the immobilization of penicillin G acylase(PA). The effects of the amount of the crosslinking agent on the structure properties and the apparent activity of immobilized enzyme were investigated. The specific surface area of GNM copolymer increased, its average pore diameter and pore volume decreased, and swelling degree in water increased and then decreased with increasing the amount of the crosslinking agent. The apparent activity of 625 U/g(dry weight) was obtained when the enzyme immobilized on GNM polymer [m(NVP)/m(GMA)=1/5, {w(MABB)=}40%] with a mean pore diameter of 16.5 nm, an oxirane group content of 0.906 mmol/g and swelling degree of 203% in water. The optimal pH value and temperature of the hydrolysis of penicillin G over the immobilized enzyme was 8.0 and 50 ℃, respectively. The immobilized enzyme was kept at 4 ℃ for 40 d, the change of the activity was not observed.The apparent activity of the immobilized enzyme reached a relatively steady value(about 601 U/g) after the immobilized enzyme was used for the hydrolysis of penicillin G for 3 times at 37 ℃. It was used continuously and repeatedly for 12 times, the activity was hardly changed.

Key words: Oxirane, Hydrophilic support, Inverse suspension polymerization, Penicillin acylase, Immobilization