Medium optimization for a novel 58 kDa dimeric keratinase from Bacillus licheniformis ER-15: Biochemical characterization and application in feather degradation and dehairing of hides

A novel dimeric 58 kDa keratinase is reported from Bacillus licheniformis ER-15. The bacterium produced 244 U/ml keratinase in 48 h which was increased by eight fold (1962 U/ml) after medium optimization by one-variable-at-a-time and response surface methodology. Enzyme was concentrated by ultrafiltration followed by acetone precipitation and purified by gel filtration chromatography. It had subunit of 30 and 28 kDa and pI of 8.4. Enzyme was maximally active at pH 11 and 70 °C. It hydrolyzed various complex proteins viz. haemoglobin, feather, hooves, fibrin and meat protein. It was a thiol activated serine protease and 6.25-fold enhancement in activity was observed in presence of 5 mM mercaptoethanol. Nearly 1200 U keratinase degraded 1.5 g feather in 12 h at pH 8, 50 °C in redox free environment. This enzyme also dehaired buffalo hide within 16 h in presence of 3% Ca (OH)2.