Microbial Valorization of Tannery Waste: Production and Physicochemical Characterization of a Highly Stable Alkaline Protease

The global leather industry generates significant volumes of tannery wastes, creating conducive niche for the proliferation of proteolytic microbes. The study investigated microbial valorization of tannery waste through production and physicochemical characterization of a highly stable alkaline protease. Over 100 bacterial strains were isolated from the aqueous waste of Awash Tannery. Among these, 22 isolates were exhibited visible distinct clear zones around the colonies. Out of 22 bacterial strains, YATW18 was identified as the most efficient producer of extracellular alkaline protease; with 92.65 U/mL Activity at 48h. Molecular identification based on 16S rRNA gene sequence identified the strain YATW18 as Alkalihalophilus pseudofirmus. Physicochemical characterization of alkaline protease showed optimum activity at 55℃ and pH 10. The enzyme reached its saturation level within 20 min of incubation time and then linear activity was observed until 45 min. The enzyme activity of alkaline protease demonstrated a notable tolerance to increasing salt concentrations. Most metal ions had minimal influence on protease activity across concentrations, with the relative activity close to 100%. Overall, this study showed microbial valorization of tannery waste and its huge potential to be used as a key source of efficient and stable alkaline protease.