Biochemical Engineering Journal, vol.14, no.2, pp.117-126, 2003 (SCI-Expanded)
Invertase was covalently immobilised on the poly(hydroxyethyl methacrylate-co-glycidyl methacrylate) (poly(HEMA-GMA)) film. The invertase immobilisation capacity of the films was increased as the GMA ratio increased in the film structure. The immobilised invertase on the poly(HEMA-GMA-3) composition exhibited an activity of 32.7 U cm-2 film. The optimum temperature of the immobilised invertase increased by 5 °C, and the optimal pH values for the free and the immobilised enzymes were determined as 5.0. The retained activity of the immobilised invertase was between 53 and 85%. Kinetic parameters were determined for immobilised invertase as well as for the free enzyme. The values of the Michael's constant Km of invertase were significantly larger, ca. 2.7 times upon immobilisation, indicating decreased affinity by the enzyme for its substrate, whereas Vmax was smaller for immobilised invertase. Activity of the immobilised invertase was quite stable with respect to free counterpart. After 168 h reaction, only 8% of immobilised invertase activity was lost. The operational inactivation rate constant (kopi) of the immobilised invertase at 35 °C with 200 mM sucrose was 8.23 × 10-6 min-1. © 2002 Elsevier Science B.V. All rights reserved.