Purification and characterization of a keratinolytic protease produced by probiotic Bacillus subtilis

Microbial biodegradation of waste feathers constitute an alternative to convert hard proteins into valuable products through non-polluting processes. The probiotic Bacillus subtilis FTC02PR1 demonstrated efficiency for degradation of feather meal, white feathers and melanized feathers. Only a few reports describe the microbial degradation of highly resistant melanized feathers. Human hair, a source of pure α-keratin, was poorly degraded. A keratinolytic protease produced by this strain was purified by liquid chromatography on Sephadex G-75 and DEAE Sepharose. The enzyme was characterized as a serine proteinase with approximately 30 kDa, and optimal activity at 60 °C and under a broad pH range 6.0–11.0). Thermal tolerance at 55 °C was significantly increased in the presence of manganese ions. This enzyme may be useful for hydrolysis of recalcitrant proteins. The production of keratinases by probiotic bacterial strains may concomitantly allow better use of keratin-based feeds, due to the possibility of diet supplementation with beneficial microorganisms.