The magnetic polyvinylalcohol (PVAL) microspheres were prepared by crosslinking glutaraldehyde. 1,1 ' -Carbonyldiimidazole (CDI), a carbonylating agent was used for the activation of hydroxyl groups of polyvinylalcohol, and invertase immobilized onto the magnetic PVAL microspheres by covalent bonding through the amino group. The retained activity of the immobilized invertase was 74%. Kinetic parameters were determined for immobilized invertase, as well as for the free enzyme. The K-m values for immobilized invertase (55 mM sucrose) were higher than that of the free enzyme (24 mM sucrose), whereas V-max values were smaller for the immobilized invertase. The optimum operational temperature was 5 degreesC higher for immobilized enzyme than that of the free enzyme. The operational inactivation rate constant (k(opi)) of the immobilized invertase at 35 degreesC with 200 mM sucrose was 5.83 x 10(-5) min(-1). Thermal and storage stabilities were found to increase with immobilization. (C) 2001 Elsevier Science Ltd. All rights reserved.