Immobilization of catalase onto clays

The immobilization characteristics of catalase onto bentonite and sepiolite were investigated and the relative activities of free and immobilized catalases were examined under varying experimental conditions. The effects of various factors such as concentration of catalase solution, pH, temperature and ionic strength were observed on both immobilization ratio and its relative activity. Experiments were done on free and immobilized catalases concerning the determination of thermal stability, storage stability, operational stability and kinetic parameters. It was determined that optimum temperature, pH and ionic strength for free and immobilized catalases are 35ºC, pH 7 and 50 mM (for free catalase) and 35ºC, pH 8 and 50 mM (for immobilized catalases), respectively. The increased resistance of the immobilized catalase against the changes of temperature, pH and ionic strength indicates that immobilizing catalase onto bentonite and sepiolite is useful. The changes of kinetic parameters were observed and discussed. It was observed that the storage stabilities of immobilized catalases were better than free catalase, and immobilized catalases showed an operational stability. The adsorption kinetics was interpreted using pseudo-first-order kinetic model and pseudo-secondorder kinetic model. The pseudo-second-order model provides the best correlation with the experimental data of catalase adsorption. The adsorption data could be fitted with Freundlich and Langmuir equation to find the characteristic parameters of each model. In conclusion, clay materials can be alternative and low cost material for catalase immobilization.