Purification and Some Properties of Keratinase from Bacillus licheniformis Strain NBRC 14206

Abstract

Keratinases are extracellular enzyme used for the biodegradation of keratin and hydrolyze both native and denatured keratin. They have potential roles in biotechnological processes involving keratin containing wastes from poultry and leather industries. This study investigated the purification and characterization of a keratinase from Bacillus licheniformis strain. The enzyme was purified using ammonium sulphate precipitation, carboxyl methyl cellulose and gel filtration on Sephadex G75. The purified keratinase was characterized by assessing the influence of various physicochemical parameters (temperature, pH, metal ions, inhibitors and substrate concentrations) on the activity and stability of the enzyme. The crude enzyme was purified using three purification steps (ammonium sulphate, carboxyl methyl cellulose and Sephadex G75 filtration) with 10-fold purification and 3.46% yield. The result obtained revealed that the optimum pH of activity and stability were at pH 9.0 while optimum temperature was 40ºC. The purified keratinase was stable at 40ºC. The enzyme activity was slightly stimulated by Ca2+, Zn2+ and Fe2+ while EDTA had the highest stimulatory effect on the purified keratinase. The enzyme was strongly inhibited by H202, PMSF and Hg in decreasing order suggesting that it belongs to the family of serine proteases. Results obtained from this study suggest the keratinase produced from B. licheniformis strain as promising candidate in enzymatic feather degradation and could find application in leather, pharmaceutical and cosmetics industries.