Characterization of a keratinase produced by Bacillus sp. P7 isolated from an Amazonian environment

The Amazonian bacterium Bacillus sp. P7 efficiently degraded feather keratin during submerged cultivations, producing extracellular keratinolytic enzymes. Keratinase produced during growth on feather meal broth was partially purified by ammonium sulphate precipitation, gel filtration, and ion-exchange chromatography, resulting in a purification factor of 29.8-fold and a yield of 27%. Zymography revealed two proteolytic bands, mainly inhibited by phenylmethylsulfonyl fluoride (PMSF). Partially purified keratinase had optimal activity at 55 °C and pH 9.0, was stimulated by Ca2+ and Mg2+, and was inhibited by Hg2+, Cu2+ and Zn2+. Organic solvents 2-mercaptoethanol and Triton X-100 slightly affected the enzyme activity, whereas SDS stimulated it. PMSF and ethylenediaminetetraacetic acid (EDTA) inhibited proteolytic activity, which suggests its serine-protease feature, with the requirement of metal ions for maximum activity and/or stability. Alkaline keratinase might be employed in detergent formulations, in leather processing, and in other processes involving protein hydrolysis. The maintenance of enzyme activity in the presence of reducing agent (2-mercaptoethanol) makes this partially purified keratinase interesting for application in the breakdown of recalcitrant keratin wastes.