Wool-waste valorization: production of protein hydrolysate with high antioxidative potential by fermentation with a new keratinolytic bacterium, Bacillus pumilus A1

Aims: Wool, a recalcitrant waste mainly composed of keratin, constituted a serious problem for the environment and was not effectively valorized. This study reported the optimization of wool-waste biodegradation by a new keratinolytic bacterium Bacillus pumilus A1. The in vitro digestibility and the antioxidant potential of wool protein hydrolysate (WPH) were also investigated. Methods and Results: The antioxidant potential of WPH was evaluated using in vitro antioxidant assays, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity, reducing power and metal (Fe2+) chelating activity. Cultivation on 50 g l(-1) of wool for 2 days, at 45 degrees C and at initial pH of 10, resulted in maximum production of amino acids and peptides (39.7 g l(-1)). WPH presented a very high in vitro digestibility (97%) as compared with that of the untreated wool (3%). Conclusions: The keratin present into the wool-waste was completely solubilized. Interestingly, WPH presented an important DPPH radical-scavenging activity with an IC50 value of 0.14 +/- 0.01 mg ml(-1). Significance and Impact of Study: WPH would be a very useful source of protein and antioxidants in animals' diets.