Production and characterization of keratinase enzymes from Alcaligenes faecalis and Pseudomonas aeruginosa isolated from decayed fish scales

Keratinases are enzymes that catalyze the degradation of keratin, a resilient protein found in various biological materials such aseathers, hair, and fish scales. Two isolates identified from previous work as Alcaligenes faecalis (SCA A1) and Pseudomonas aeruginosa (FSA A2) was used for keratinase production. The enzyme produced were purified using dialysis, ion exchange chromatography and gel filtration chromatography and the purified enzyme was characterized and used to check for keratin substrate specificity. Fermentation studies revealed that A. faecalis (SCA A1) displayed optimal growth at pH 9.5 and 10.5, particularly at higher temperatures (48°C, 58°C, and 68°C) when using Mackerel fish scales as the substrate. In contrast, P. aeruginosa (FSA A2) demonstrated better growth at pH 7.5 and 8.5, with the highest growth observed at 28°C and 38°C using both Mackerel and Elephant fish scales. Enzyme activity profiles showed that A. faecalis exhibited higher activity with Mackerel scales (65.7 U/ml), while P. aeruginosa showed greater activity using Elephant scales (68.1 U/ml). Purification of the keratinase enzymes from both isolates resulted in a 7-fold increase in specific activity, reaching 35.16 U/mg for A. faecalis and 37.80 U/mg for P. aeruginosa. Characterization of the purified enzymes revealed that both exhibited optimal activity at 70°C, with P. aeruginosa displaying slightly higher activity. The enzymes also shows good activity over a wide pH range, with optima at pH 7.3 and 6.3 for A. faecalis and P. aeruginosa, respectively. Substrate specificity analysis indicated that both enzymes had the highest activity towards Mackerel fish scales, followed by Casein, Human Hair, Chicken feathers, and Elephant fish scales. These findings highlight the potential of A. faecalis and P. aeruginosa for the biodegradation of fish scale waste, offering a sustainable solution for waste management and the production of valuable bioproducts. These results suggest that these keratinolytic bacteria could be utilized in the development of bioremediation strategies for fish processing waste. Additionally, the keratinase enzymes produced by these isolates could be utilized in various industrial applications, such as the production of animal feed supplements, leather processing, and the development of cosmetic and pharmaceutical products.