Abstract

Here, we report a new keratinolytic-producing bacterium identified as Bacillus halotolerans 4BC based on 16S rRNA gene sequencing. 4BC strain isolated from a tannery wastewater, showed proteolytic activity when grown on keratin azure, bovine hair and feather meal agar plates. B. halotolerans 4BC degraded almost 88% of chicken feathers after 10 days of cultivation in feather powder broth at pH 8 and 37°C. It was also efficiently able to degrade bovine hair keratin, despite the complexity of this substrate in comparison to feather keratin. The effects of different liquid to substrate ratios, inoculum sizes and incubation times on keratinase production were studied using response surface methodology to find the optimum conditions required for maximum B. halotolerans keratinase yield. The maximum keratinase yield (1059±53 mU/ml) was found under the following conditions: incubation period of 10 days, liquid/solid ratio of 5 and inoculum size of 2.3 % v/v). The crude enzyme exhibited a remarkable activity and stability under high temperature and alkaline conditions (pH 10 at 80°C). Additionally, the touch-visual and histological results demonstrated that the enzyme treated dehaired hides exhibit similar or improved characteristics without damaging the collagen layer, which makes the crude keratinase a potential effective and eco-friendly candidate for application in leather industry to avoid pollution problems associated with the use of chemicals.

Keywords

bacillus halotolerans, tannery wastewater, extremophilic keratinase, hide dehairing, feather degradation