Immobilization of Candida rugosa lipase onto spacer-arm attached poly(GMA-HEMA-EGDMA) microspheres

Epoxy group-containing poly(GMA-HEMA-EGDMA) microspheres were prepared by suspension polymerisation. The epoxy groups of the poly(GMA-HEMA-EGDMA) microspheres were used for the covalent attachment of Candida rugosa lipase and 1,6-diaminohexane (i.e., spacer-arm). C. rugosa lipase was also covalently immobilised onto the spacer-arm-attached poly(GMA-HEMA-EGDMA) microspheres using glutaric dialdehyde as a coupling agent. The maximum lipase immobilization capacities of the poly(GMA-HEMA-EGDMA) and poly(GMA-HEMA-EGDMA)-spacer-arm attached microspheres were 16.1 and 28.3 mg g−1, respectively. The attachment of the spacer-arm resulted in an increase in the apparent activity of the immobilised lipase with respect to the enzyme immobilised via the epoxy groups of the microspheres. The activity yield of the lipase immobilised on the spacer-arm attached microspheres was up to 45%, and this was 9% for the enzyme immobilized through epoxy groups. Therefore, the rest of the immobilization study was carried out using only spacer-arm attached microspheres. The optimum temperature for lipase immobilised on the spacer-arm attached microspheres was 5 °C higher than that of the free enzyme and was also significantly broader. The immobilised lipase had better resistance to temperature inactivation than did the free form.