Magnetic polyvinyl alcohol (PVA) microspheres with 8—64 μm in diameter were prepared from PVA by dispersion and copolymerization with Fe3O4 as magnetite.There were more functional groups

such as hydroxyl and carboxyl etc. on the microsphere surface.1

1′-Carbonyldiimidazole (CDI)

a carbonylating agent

was used for the activation of hydroxyl groups of PVA

and α-acetolactatedecarboxylase (ALDC) was immobilized onto the magnetic PVA microspheres by covalent bonding through the amino group.The results showed that total activity

protein binding

specific activity and activity retention of the immobilized enzyme were 63293 U·g-1

72.67 mg·g-1

870.96 U·mg-1and 48.71％

respectively.The optimum temperature of immobilization enzyme was 50℃ and the optimum pH was 6.0.Compared with the free enzyme of ALDC

the thermal

operational and pH stability of the immobilized enzyme were improved.After being stored at 4℃

pH 6.0 for 31 days

the immobilized ALDC retained 95.7% of its initial activity which was 8% higher than the free enzyme.