Abstract
Keratinase has the ability to degrade the recalcitrant keratinous wastes that cannot be degraded by conventional proteases. The present study describes a novel hyperstable keratinolytic enzyme from Bacillus sp. NKSP-7, which has excellent efficiency of keratin-feather biodegradation, washing and dehairing. The production of extracellular keratinase was improved by 3.02-fold through optimization of various parameters. Purified keratinase (25 kDa) showed optimal activity at 65 °C and pH 7.5, and displayed stability over a range of pH (5.5–9.5) and temperature (20–60 °C) for 8 h. No conspicuous effect was perceived with various chemicals and organic solvents, however, the catalytic efficiency was enhanced in the presence of Ca2+, Cd2+, Na+, Mn2+, sodium sulfite, and β-mercaptoethanol. The enzyme was completely inhibited by phenylmethanesulfonyl fluoride (PMSF), suggesting that this keratinase belongs to serine protease family. It displayed prodigious stability and compatibility to salinity and commercial detergents. Enzyme exhibited great substrate specificity but high affinity was observed with keratin-rich substrates. Crude and purified keratinase revealed perceptible potential for destaining of blood-stained fabric (10 min), and dehairing of hide (8 h) without any damage. All these auspicious features make this enzyme a promising candidate for various industrial applications, especially in keratin-waste management, detergent formulations and leather processing.
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