Kinetics and Isotherm Studies of the Immobilized Lipase on Chitosan Support

The kinetics and isotherm studies of the immobilized lipase and the mechanism of immobilization onchitosan beads and activated chitosan beads with glutaraldehyde were investigated. The validity ofexperimental data fitted to Langmuir, Freundlich, Hill, Sips, Temkin, Redlich-Paterson and Dubinin-Radushkevich isotherm models for both immobilization methods were examined. The isotherm modelswere compatible and confirmed immobilization techniques. In comparing of the isotherm models, thebest fit of experimental data was obtained by Langmuir isotherm model for chitosan beads; which isconsistent 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 byglutaraldehyde so that it can reveal the multilayer adsorption. Also, pseudo-first order, pseudo-secondorder, Elovich and intra-particle diffusion were studied by experimental results in differentconcentration of lipase. Pseudo-first order kinetic model were described immobilization of lipase onchitosan beads and corresponds to physical adsorption of enzyme on the carrier. In fact, activatedbeads have followed pseudo-second order kinetic model which is indicated that chemical adsorption ofenzyme occurred in the carrier. In addition, intra-particle diffusion equation for chitosan beads andactivated chitosan beads is properly fitted by experimental data with high regression coefficient. Inaddition, FESEM analysis of chitosan beads and activated chitosan beads demonstrated thatglutaraldehyde has significantly enhanced the surface porosity of chitosan beads. Maximum capacityof immobilization was enhanced by 2 folds, when the porosity of chitosan beads were improved byglutaraldehyde. These results were confirmed with adsorption isotherm models and kinetic equations.