Production and biochemical characterization of alkaliphilic keratinase from Vibrio sp. strain R11 with potential biotechnological applications

Abstract

Keratinases are industrially important enzymes with applications in waste management, leather processing, and detergent formulations. However, the demand for enzymes that remain active and stable under extreme alkaline conditions continues to grow. Alkaliphilic microorganisms from extreme environments such as soda lakes represent promising sources of such robust enzymes. Therefore, this study aimed to isolate and characterize an alkaliphilic bacterial keratinase from Ethiopian soda lakes with potential biotechnological applications. An alkaliphilic Vibrio sp. strain R11 (Accession number OK605557) was isolated and screened for keratinolytic activity using hair as the sole source of carbon and nitrogen. The enzyme was produced under alkaline conditions and characterized with respect to pH, temperature, effect of metal ions, inhibitor sensitivity, and stability in detergents, surfactants, and organic solvents. Its practical applicability was further evaluated through stain removal and dehairing assays. The strain completely hydrolised hair, demonstrating strong keratinolytic capability. The keratinase was active over a wide range of alkaline pH values (7.5-12), retaining over 30% of its maximum activity at pH 12 and 40 ^oC for 1 h, with optimal activity at pH 11. The enzyme was Ca²⁺ dependent for its activity and stability, especially at higher temperature values and was inhibited by a serine protease inhibitor, Phenylmethylsulfonyl fluoride. The enzyme was stable in detergents, surfactants and organic solvents. This enzyme efficiently removed blood and egg yolk stains at 11.6 U/mL keratinase within 30 min of incubation at 37 ^oC and completely dehaired sheepskin after overnight incubation. The amount of total soluble proteins obtained from the hydrolysis of hair was 3.088 mg/mL. These enzyme properties make this strain and the keratinase it produces a promising candidate for biotechnological applications, especially in the leather and detergent industries. This enzyme can also be a potential candidate for the production of essential amino acids and peptides from cheap, readily available keratinous waste thus providing an efficient means of waste management.