Screening of Bacteria for Protease Production and Feather Degradation

Feathers are recalcitrant wastes produced by the poultry industry. Considering potential environmental hazards and the need for energy conservation/recycling, adequate approaches are demanded for feathers reclamation. Microbial conversion is an interesting alternative from both technological and economical perspectives. Therefore, 15 bacterial strains were isolated from a site containing waste feathers, and evaluated for proteolytic and keratinolytic potentials. From these bacterial isolates, seven produced extracellular proteases in milk agar plates, also demonstrating the ability to grow on feather meal agar plates, preferentially at pH values from 7 to 9, and at 30-37 degrees C. The isolate named CL33A displayed higher efficiency for feather degradation in qualitative assays, and selected for studies in feather broth (FB), a medium containing whole feathers (10 g/L) as the sole source of carbon, nitrogen and energy. CL33A degraded 29, 75, and 95 % of the feathers in FB, after 96, 144 and 216 h of growth, respectively. Feather degradation was corroborated by increases in soluble protein concentration and medium pH. Production of proteolytic enzymes reached maximal values after 216-240 h of growth on FB, and CL33A also produced proteases when cultivated in feather meal, peptone, and soy protein isolate. Through 16S rRNA gene sequencing, this feather-degrading isolate was identified as Bacillus sp. CL33A. Bioprocessing could be a suitable technology aiming the management and valorization of feathers/feather meal, due to the production of protein hydrolysates and also proteolytic enzymes that could be used as important biocatalysts.