Covalent immobilization of lipase onto hydrophobic group incorporated poly(2-hydroxyethyl methacrylate) based hydrophilic membrane matrix Original Research Article

In this study, a hydrophobic group containing monomer, 2-methacrylamidophenyalanine (MAPA) was prepared by using methacrylochloride and phenylalanine. Then, poly(2-hydroxyethyl methacrylate-co-methacrylamido-phenlyalanine) (pHEMA-MAPA) membranes were prepared by UV-initiated photopolymerization of HEMA and MAPA in the presence of an initiator α-α′-azobisisobutyronitrile (AIBN). The lipase was immobilized onto these membranes by covalent bonding through carbodiimide activation. The amount of enzyme loading on the membranes was increased as the MAPA ratio increased in the membrane structure. Immobilization improved the pH stability of the enzyme as well as its temperature stability. Thermal stability was found to increase with immobilization and at 60 °C the thermal stability constants were 1.1×10−1min for free enzyme and 1.2×10−2min for the immobilized enzyme. The immobilized enzyme activity was found to be quite stable in repeated experiments.