Valorization of refractory keratinous waste using a new and sustainable bio-catalysis

Abstract Keratinous materials, the third most abundant polymer in nature after cellulose and chitin, are resistant to degradation by chemical and biological hydrolysis. Conventional biocatalytic conversion of refractory keratinous waste has its intrinsic limitations and disadvantages, such as low-activity and high cost of biocatalysts, being time-consuming, and low yield of value-added bio-based products. In the present work, a novel and simple route for high-efficiency biocatalysis of feather wastes is proposed, using proteolysis with HDSF-assisted conventional protease. This route effectively eliminates the need for substrate-specific keratinases, as it only uses cheap proteases (conventional proteases) to degrade 95% of the feather substrate within 2 h. Thereby, more than 0.8 g of high-value nutrients and bioactive molecules, such as peptides with antidiabetic, anti-hypertension, and antioxidant activities, were produced from 1 g of feather wastes. In addition, different hydrolysis models and degradation mechanisms of keratinolysis and proteolysis of keratins were investigated to gain further insight into the hard-to-degrade biomass-valorization technology. This method can efficiently convert cheap feather wastes into value-added bioproducts in an industrial scale.