Bentonite and sepiolite as supporting media: Immobilization of catalase

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 degrees C, pH = 7 and 50 mM (for free catalase) and 35 degrees C, pH = 9 and 50 mM (for both immobilized catalases), respectively. K-m and V-max values were 116.8 mM and 30.1 mu mol min(-1) mg protein(-1) for free catalase, 55.6 mM, V-max = 6.6 mu mol min(-1) mg protein(-1) for bentonite supported catalase and K-m = 49.2 mM, V-max = 8.7 mu mol min(-1) mg protein(-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 1 h preincubation time at 45 degrees C. Both immobilized catalases showed an operational stability and for a period of 10 cycles of experiments they lost only 34.4% and 9.8% of their initial activities for bentonite and sepiolite immobilized catalases, respectively.