Kinetic properties and storage stability of catalase immobilized on to florisil

Abstract

The covalent immobilization of bovine liver catalase (CAT) on to florisil via glutaraldehyde was investigated. Optimum immobilization pH and temperature were determined as pH 6.0, 10°C respectively, while the amount of initial CAT per g of carrier and immobilization time was determined as 5 mg g⁻¹ and 120 min, respectively. The Vmax values for free and immobilized CAT were found to be 1.7 × 10⁵ and 2.0 × 10⁴ μmol H₂O₂. min⁻¹ mg protein⁻¹, respectively, whereas KM values were 33.3 mM and 1722.0 mM respectively. Operational stability was determined by using a stirred batch-type column reactor. Immobilized CAT retained about 40% of its initial activity after 50 uses. It showed higher storage stability than free CAT at 4°C and 25°C. Its storage stability increased with increasing relative humidity (RH) from 0 to 20% of the medium. The highest storage stability was obtained in 20% RH, however, further increase in RH from 40 to 100% significantly decreased the storage stability.