Bentonite and sepiolite as supporting media: Immobilization of catalase

Abstract

Immobilization of catalase onto bentonite and sepiolite was studied as a function of pH, temperature and ionic strength for free and immobilized enzyme activities. The optimum temperature, pH and ionic strength for free and immobilized catalases were 35°C, pH=7 and 50mM (for free catalase) and 35°C, pH=9 and 50mM (for both immobilized catalases), respectively. Km and Vmax values were 116.8mM and 30.1μmolmin−1mgprotein−1 for free catalase, 55.6mM, Vmax=6.6μmolmin−1mgprotein−1 for bentonite supported catalase and Km=49.2mM, Vmax=8.7μmolmin−1mgprotein−1 for sepiolite supported catalase. The storage stabilities of immobilized catalase were higher than free catalase. Free catalase lost 50.7% of its initial activity, while sepiolite immobilized catalase lost 41.1% and bentonite immobilized catalase lost only 32.6% of their initial activities for 1h preincubation time at 45°C. Both immobilized catalases showed an operational stability and for a period of 10cycles of experiments they lost only 34.4% and 9.8% of their initial activities for bentonite and sepiolite immobilized catalases, respectively.Batch adsorption studies were also carried out to determine the kinetic parameters. The pseudo second order model provided the best correlation with the experimental results.