A feather-degrading bacterium with high keratinase activity was isolated and identified as Bacillus licheniformis YJ4. After 72 h incubation in a medium (0.5% feather meal, 0.05% NH4Cl and NaCl, 0.04% K2HPO4, 0.03% KH2PO4, 0.01% MgCl2 and yeast extract, 0.1% rice husk) at 37°C, 2 keratinases (keratinase I and II) were purified to electrophoretical homogeneity by CM sepharose and Sephadex G-75 chromatographs. They were with molecular masses (M) of 35.5 and 32.8 kDa, isoelectric point (pI) of 6.63 and 6.50, respectively, and stable at pH 6.0-10.0 and 10-50°C. The optimal pH and temperature were similar, at 9.0 and 60°C, respectively. According to the effect of metal, inhibitor and reducing agent, and previous studies, the purified keratinases I and II were considered to be cysteine and serine proteases, respectively.

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