Keratinolytic proteinase from Bacillus thuringiensis AD-12

A new isolated strain noted to produce a novel detergent-stable serine keratinolytic proteinase and identified as Bacillus thuringiensis AD-12. Native keratinolytic proteinase from B. thuringiensis (BtKER) was purified and characterized. The purified BtKER enzyme is a monomer with a molecular mass of 39 kDa. Biochemical characterization assays revealed that the BtKER attained optimal activity at pH 7 and 30 °C. Residual activity after 1 h incubation at 50 °C was higher than 80%. The enzyme was activated and stabilized by Mn2+ and Li+ metal ions but inactivated by organic solvents. Purified BtKER showed the highest substrate specificity toward keratin from wool > sodium caseinate > collagen > BSA > gelatin in descending order. BtKER is the first reported keratinolytic proteinase from B. thuringiensis and obtained results suggested that new characterized enzyme can be a powerful biocatalyst in peptide production associated to hydrolysis of keratinous and/or keratin-like waste.