In-Situ and Cell-Free Goat Hair Hydrolysis by a Consortium of Proteases from Bacillus licheniformis Strain ER-15: Hair Hydrolysate Valorization by Melanin Extraction

Purpose Animal hair waste is one of the most abundant solid wastes generated from the agro-industries. The keratinolytic microbes and their enzymes can be employed for rapid degradation of solid waste to reduce environmental pollution and to recover value-added products. Methods In-situ hydrolysis of goat hair and simultaneous production of proteases from Bacillus licheniformis strain ER-15 during submerged fermentation. Utilization of crude extracellular extract for the depilation of goat hides, and bioconversion of goat hair into valuable products like protein hydrolysate and melanin pigment. Results Production of proteolytic enzymes from B. licheniformis strain ER-15 was enhanced by 7.72-fold (747.35 U/mL) through medium optimization strategies in the presence of goat hair as one of the main substrates. Proteomics analysis using liquid chromatography with tandem mass spectrometry (LC–MS/MS) revealed the presence of a consortium of proteases, peptidases, and hydrolases in the culture supernatant. The application of cell-free crude extract allowed lime and sulfite-free hide dehairing in 48 h at ambient temperature. The same enzyme formulation was subsequently used to hydrolyze depilated hair, preceding mild-alkali treatment, and resulted in 74% weight reduction overnight. The value-added by-product, melanin, was extracted and purified from the hair hydrolysate with suggested applications in the cosmetics and pharmaceutical industries. Conclusion The process presented here provides an efficient enzymatic way of solid waste mitigation and management of goat hair, a hard-to-degrade keratinous waste. Moreover, the developed procedure would result in a significant reduction in effluent generation and could provide a way forward towards green technology. Graphical Abstract