Hydrolysis of sucrose by invertase immobilized onto novel magnetic polyvinylalcohol microspheres

The magnetic polyvinylalcohol (PVAL) microspheres were prepared by crosslin king glutaraldehyde. 1,1 ' -Carbonyldiimidazole (CDI), a carbonylating agen t was used for the activation of hydroxyl groups of polyvinylalcohol, and i nvertase immobilized onto the magnetic PVAL microspheres by covalent bondin g through the amino group. The retained activity of the immobilized inverta se was 74%. Kinetic parameters were determined for immobilized invertase, a s 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), wher eas V-max values were smaller for the immobilized invertase. The optimum op erational temperature was 5 degreesC higher for immobilized enzyme than tha t of the free enzyme. The operational inactivation rate constant (k(opi)) o f the immobilized invertase at 35 degreesC with 200 mM sucrose was 5.83 x 1 0(-5) min(-1). Thermal and storage stabilities were found to increase with immobilization. (C) 2001 Elsevier Science Ltd. All rights reserved.