Invertase reversibly immobilized onto polyethylenimine-grafted poly(GMA-MMA) beads for sucrose hydrolysis

The epoxy group containing poly(glycidyl methacrylate-co-methyl methacrylate) poly(GMA-MMA) beads were prepared by suspension polymerisation and the beads surface were grafted with polyethylenimine (PEI). The PEI-grafted beads were then used for invertase immobilization via adsorption. The immobilization of enzyme onto the poly(GMA-MMA)-PEI beads from aqueous solutions containing different amounts of invertase at different pH was investigated in a batch system. The maximum invertase immobilization capacity of the poly(GMA-MMA)-PEI beads was about 52 mg/g. It was shown that the relative activity of immobilized invertase was higher then that of the free enzyme over broader pH and temperature ranges. The Michaelis constant (K-m) and the maximum rate of reaction (V-max) were calculated from the Lineweaver-Burk plot. The K-m and V-max values of the immobilized invertase were larger than those of the free enzyme. The immobilized enzyme had a long-storage stability (only 6% activity decrease in 2 months) when the immobilized enzyme preparation was dried and stored at 4 degrees C while under wet condition 43% activity decrease was observed in the same period. After inactivation of enzyme, the poly(GMA-MMA)-PEI beads can be easily regenerated and reloaded with the enzyme for repeated use. (c) 2005 Elsevier B.V. All rights reserved.