Immobilization of lipase from Candida rugosa into copolymer hydrogels of poly(N-isopropylacrylamide-co-itaconic acid) synthesized in the presence of surfactants

To overcome the problems of free enzyme application as catalysts in chemical reactions, i.e. high costs of isolation and purification processes, high sensitivity to process conditions, insufficient enzyme stability etc., a different immobilization techniques are to be used. Immobilization to/within solid support improves enzyme stability decreasing its denaturation. This paper deals with hydrogels of N-isopropylacrylamide and itaconic acid with incorporated nonionic surfactants (Triton X-100, Brij 30 and Tween 80) synthesized in distilled water at room temperature by free radical polymerization. These hydrogels were used as supports for immobilization of enzyme, lipase from Candida rugosa by post-entrapment method. The aim was to investigate the effect of the nonionic surfactants on the lipase binding capacity, as well as on its hydrolytic activity. In order to characterize the obtained hydrogels FT-IR analysis has been performed. Further, the swelling behaviour of these samples in buffer solution of pH 6.80 has been investigated. The dynamic - mechanical properties of hydrogels and detailed have been studied, too. The immobilized lipase showed somewhat reduced hydrolytic activity, as compared to the activity of free lipase as well as in comparison to the lipase immobilized to the reference sample (sample synthesized under the same polymerization conditions, but in the absence of surfactants). It was concluded that the addition of surfactants increased the hydrogel mesh size. The surfactant addition did not affect the dynamic - mechanical properties of the investigated hydrogels. The largest percentage of specific activity and yield of activity were presented by the reference sample, too. It is obvious that the absence of surfactants charged groups has no influence on the lipase binding capacity, and the obtained activity yields are to be expected.