Keratinase

Keratinase is a proteolytic enzyme capable of degrading keratin, a hard, insoluble protein abundant in feathers, hair, nails, horns, and hooves. Keratinases are produced by a range of microorganisms, notably Bacillus species such as Bacillus licheniformis and Bacillus subtilis, as well as filamentous fungi including Aspergillus and Chrysosporium. Many keratinases are extracellular serine proteases with keratinolytic activity, though other proteases with keratin-degrading capability have been reported.

Keratin’s resilience stems from extensive disulfide cross-links and a compact, fibrous structure. Keratinases often act in conjunction with reducing agents or accessory enzymes that break disulfide bonds, enabling cleavage of keratin peptide chains. They can target both alpha-keratin and beta-keratin substrates, though activity and efficiency vary with enzyme and substrate.

Applications of keratinases include the conversion of keratinous waste into usable products, such as peptide and amino acid mixtures suitable for animal feed, aquaculture, or fertilizer production. They are also explored for leather processing to aid dehairing and bating under milder conditions, as well as for inclusion in detergent formulations and in environmental bioremediation efforts.

Production methods for industrial keratinases typically involve solid-state or submerged fermentation using keratin-rich waste or specially formulated media. Strain selection and process optimization focus on improving activity at alkaline pH, thermal stability, and resistance to inhibitors. Keratinases are considered valuable for sustainable waste valorization and various industrial biotechnological applications.