Abstract: A neutral protease from Balilius Subtilis has been immobilized onto the magnetic polymer microspheres,which were obtained from styrene,hydroxyethyl methacrylate,divinyl benzene and Fe₃O₄,and had hydroxyl groups in the surface by covalent coupling.The magnetic immobilized neutral protease had a enzyme activity of 1000U/g,enzyme yield of 20～30mg/g carrier,and activity retention of about 40%.For both free enzyme and immobilized enzyme the optimum work temperatures were 50℃ and 50～60℃,the optimum pH values were 7.5 and 6.5, and the kinetic constants were 0.054% and 0.088%,respectively.The thermal stability, pH stability,and the storage stability of the immobilized enzyme are improved obviously.

Key words: magnetic polymer microsphere, neutral protease, immobilization