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.
Covalent immobilization of lipase from Candida rugosa on Eupergit®