Abstract

In this study, chitosan polymer was modified in two different ways and used for the immobilization of bovine liver catalase (CAT). First, it was activated with glutaraldehyde (GAL), and then covalently immobilized covalently onto the support via lysine amino acid residue in CAT. In the second modification, GAL-activated chitosan was interacted with polylysine (pLYS), then reactivated with GAL and used in CAT immobilization. Samples of bare chitosan (Chi), GAL-activated (ChiGAL), polylysine-modified (ChiGAL-pLYS), reactivated with GAL (ChiGAL-pLYSGAL) and CAT-immobilized chitosan (ChiGAL -CAT and ChiGAL-pLYSGAL-CAT) were all characterized by FTIR. The enzymatic activities of Free CAT, ChiGAL -CAT and ChiGAL-pLYSGAL-CAT samples were investigated at different pH and temperatures and the values with the highest activity were determined. In addition, the effect of substrate concentration on activity under optimal conditions was investigated. Optimum pH values of Free CAT, ChiGAL-CAT and ChiGAL-pLYSGAL-CAT samples were 7.5, 7.0 and 7.0, respectively; temperature values were determined as 25, 30 and 35 C, respectively. After immobilization, the Vmax values of the enzymes decreased, the Km values increased, and the efficiency of catalase immobilized to the polylysine modified support was found to be higher. It was observed that after 20 repeatedly use in the column reactor, ChiGAL-CAT and ChiGAL-pLYSGAL-CAT enzymes retained 88 % and 76 % of their initial activities, respectively.