Co-immobilisation of superoxide dismutase and catalase using an in vitro encapsulation protocol

Abstract

The immobilisation of antioxidant enzymes using alginate gel beads has previously been reported. Upon immobilisation, the retention of enzyme activity, encapsulation efficiency and enzyme leakage from the capsules must be considered. The objective of this paper to improve the catalase (CAT) and superoxide dismutase (SOD) activity following encapsulation by co-immobilising the enzymes as a pair. CAT and SOD were partially purified from Bacillus licheniformis using (NH4)2SO4 and immobilised on beads of alginate. Further, the activities of the partially purified enzymes (both free and immobilised) were measured and characterised. The optimum pH and temperature for each of the enzymes when free and immobilised were determined. The optimum pH values for enzyme activities were 7 and 7.5 for free and immobilised CAT, respectively. The optimum temperature for activity was greater for immobilised than free enzymes. Immobilised SOD and CAT showed higher storage and thermal stabilities than free enzymes and remaining activities were about 40 and 70%, respectively, after eight cycles of use. The free CAT lost all activity within 60 days, while immobilised CAT lost 45% of its activity over a similar incubation period at 4 °C. In conclusion, we report the effects of synergistic immobilisation of the antioxidant enzymes SOD and CAT.