Synthesis of magnetic polymer microspheres and application for immobilization of proteinase of balillus sublitis

Core–shell composite magnetic polymer microspheres, containing a magnetic core and a polymer shell, were synthesized by dispersion copolymerization of styrene (St) and 2-hydroxyethyl methacrylate (HEMA) in the presence of magnetic oxide (Fe3O4) powder. The Fe3O4 powder was ultrasonically disperesed in poly(ethylene glycol) (PEG) and the affinity between the obtained superfine powder and the monomer and initator was improved. It shows that the dispersion medium and stabilizer system have a great effect on the diameter and dispersion parameter of microspheres. In the condition of controlling polymerization, the magnetic polymer microspheres containing surface OH groups, having 50–500 μm diameter and with better magnetic induction, were synthesized. The proteinase of Balillus sublitis was immobilized on magnetic polymer microspheres with an average diameter of 50–60 μm by covalent coupling. The magnetic immobilized proteinase shows an enzyme activity of 1000 U/g, the enzyme yields are usually 20–30 mg/g of carriers, and the activity retention is about 40%. The stability of the immobilized enzyme was obviously improved. © 1995 John Wiley & Sons, Inc.