Biochemical & Chemical Engineering, Noshirvani University of Technology, Babol
The kinetics and isotherm studies of the immobilized lipase and the mechanism of immobilization on chitosan beads and activated chitosan beads with glutaraldehyde were investigated. The effect of glutaraldehyde on porosity of chitosan was evaluated by FESEM analysis. It was observed that the porosity of the carrier which has activated by glutaraldehyde was substantially increased. The validity of experimental data fitted to Langmuir, Freundlich, Hill, Sips, Temkin, Redlich-Paterson and Dubini-Radushkevich isotherm models for both immobilization methods were examined. The isotherm models were compatible and confirmed immobilization techniques. Amongst the isotherm models have described experimental data, the best fit was obtained by Langmuir isotherm model for chitosan beads; which is consistent with the heterogeneous behavior of the adsorption sites on the chitosan structure. However, Freundlich isotherm model have corresponded immobilization of lipase on chitosan beads activated by glutaraldehyde so that it can reveal the multilayer adsorption. Also, pseudo-first order, pseudo-second order, Elovich and intra-particle diffusion were studied by experimental results in different concentration of lipase. Pseudo-first order kinetic model were described immobilization of lipase on chitosan beads and corresponds to physical adsorption of enzyme on the carrier. While chitosan beads activated by glutaraldehyde have followed pseudo-second order kinetic model indicating chemical adsorption of enzyme on the carrier. In addition, intra-particle diffusion equation is properly fitted experimental data for both immobilization method with high regression coefficient.