Elucidation of coding gene and characterization of alkaline metallo-keratinase produced by acidophilic Bacillus sp. Okoh-K1 grown on chicken feather

Abstract

The poultry processing industry generates a huge amount of feathers as waste. The feathers are recalcitrant to degradation, and are fraught with environmental problems. Therefore, the microbial utilization of feather biomass for the production of valuable products represents sustainable development. In this study, a keratinolytic bacteria previously isolated from a municipal waste dumpsite, and identified as Bacillus sp. Okoh-K1 was used to produced keratinase in a basal medium formulated with chicken feathers. The keratinase produced was characterized, and the gene coding for the enzyme elucidated. The optimized physico-chemical conditions were 1% (w/v) chicken feather, 0.1% (w/v) lactose, pH (4.0–6.0), temperature (30 °C) and agitation speed (150 rpm). The kinetics of keratinase production by Bacillus sp. Okoh-K1 in an optimized fermentation medium showed maximum extracellular keratinase activity of 2350.09 ± 107.99 U/mL after 48 h of fermentation. The keratinase (KerBOK1) showed optimal catalytic activity at pH and temperature of 8.0 and 60 °C, respectively; with remarkable pH and thermal stability. Ethylenediaminetetraacetic acid and 1,10-phenanthroline both inhibited the activity of KerBOK1; thus, suggesting a metallo-type of keratinase. Furthermore, the enzyme showed considerable stability upon mixture with reducing agents, organic solvents, surfactants and laundry detergents. The putative keratinase gene (kerBOK1), with band size and G+C contents of 1104 bp and 36.1% respectively, showed >90% of sequence homology with keratinase gene of Bacillus cereus group. The findings from this study suggest that both Bacillus sp. Okoh-K1 and the keratinase possess immense prospects for biotechnology and industry.