Keratinolytic activities of alkaliphilic Bacillus sp. MBRL 575 from a novel habitat, limestone deposit site in Manipur, India

Abstract

Microbial degradation of keratinous wastes is preferred over physicochemical methods as the latter is costlier and not eco-friendly. Novel habitats are promising for discovery of new microbial strains. Towards discovery of novel keratinolytic bacteria, screening of bacterial strains from a novel limestone habitat in Hundung, Manipur, India was done and a promising isolate, MBRL 575, was found to degrade native chicken feather efficiently. It could grow over a broad pH range (Langeveld et al. in J Infect Dis 188:1782–1789, 2003; Park and Son in Microbiol Res 164:478–485, 2009; Zaghloul et al. in Biodegradation 22:111–128, 2011; Takami et al. in Biosci Biotechnol Biochem 56:1667–1669, 1992; Riffel et al. in J Biotechnol 128:693–703, 2007; Wang et al. in Bioresour Technol 99:5679–5686, 2008) and in presence of 0–15 % NaCl. Based on phenotypic characterization and 16S rRNA gene sequence analysis, the new keratinolytic limestone isolate was identified as Bacillus sp. MBRL 575. It produced 305 ± 12 U/ml keratinase and liberated 120 ± 5.5 mg of soluble peptides and 158 ± 4 mg of amino acids per gram of feather after 48 h of incubation at 30 °C in chicken feather medium. The strain could also degrade feathers of other species besides chicken. The cell-free enzyme was also able to degrade feather. Citrate and soybean meal were found to be the best carbon and nitrogen supplements for enhanced enzyme, soluble peptide and amino acid production. In addition to keratinolytic activity, MBRL 575 also exhibited antagonistic activity against two major rice fungal pathogens, Rhizoctonia oryzae-sativae (65 %) and Rhizoctonia solani (58 %).