Production of keratinolytic proteases through bioconversion of feather meal by the Amazonian bacterium Bacillus sp. P45

Abstract

Extracellular keratinase production by the feather-degrading Amazonian isolate Bacillus sp. P45 was evaluated with various growth substrates. Higher enzyme production occurred with feather meal (FM) in comparison to casein, gelatin, and cheese whey, suggesting the specificity of this strain for the utilization of keratinous substrates. Supplementation of FM medium with carbohydrates reduced enzyme production, probably due to catabolite repression. Increased keratinase yield was achieved when NH4Cl was added to FM medium. The effects of FM and NH4Cl concentrations on enzyme production were investigated using a 22 central composite design. Feather meal was the most significant parameter, while NH4Cl concentrations resulted in slight differences in enzyme yield. In the range studied, optimal concentrations of FM and NH4Cl were 43–50gl−1 and 1.8–8.6gl−1, respectively, resulting in an effective low-cost medium for the production of keratinolytic protease. Crude keratinase showed maximum activity at 50°C and pH 7.0, and was strongly inhibited by EDTA, indicating the importance of metal ions for activity/stability. The crude keratinase from mesophilic Bacillus sp. P45 could potentially be used in the bioconversion of recalcitrant keratinous wastes through an environmentally friendly and energy-saving process, producing protein hydrolysates with commercial value for utilization as animal feed and fertilizers.