Immobilization of lipase using hydrophilic polymers in the form of hydrogel beads

Abstract

The purpose of this study was to immobilize lipase (triacylglycerol ester hydrolase, E.C. 3.1.1.3) from Candida rugosa using various polymers in the form of beads; to evaluate enzyme loading, leaching, and activity; and to characterize the beads. Agarose, alginate, and chitosan were the polymers selected to immobilize lipase by entrapment. Agarose beads exhibited undesirable swelling in the leaching and activity medium and the polymer was not used further. Alginate or chitosan beads were prepared by ionic gelation using calcium chloride or sodium tripolyphosphate, respectively, as the cross-linking agent in the gelling solution. Some batches of beads of each polymer were freeze dried. The results show that alginate beads leached substantially more enzyme than did chitosan beads. Entrapment efficiency, however, was the same for different chitosan levels as well as different alginate levels (43–50%). Activity in alginate was low at 240±33 and 220±26, compared to 1110±51 and 1150±11 units/ml in chitosan, for fresh and freeze-dried beads, respectively. The higher lipase activity in chitosan beads compared to that in alginate beads could be attributed to an alginate–enzyme interaction. It can be concluded that chitosan is a polymer worthy of pursuit to immobilize lipase.