Evaluation of the Nutritional and Environmental Parameters for Enhancing the Activity of Keratinase- Producing Bacteria

The production of the keratinase enzyme is one of the most promising methods for the bioremediation of feathers and has attracted increasing attention in the field of biotechnology. This study aims to enhance the production of keratinase enzymes from bacteria isolated from the soil of poultry farms in various areas of Basrah Province by optimizing nutritional and environmental parameters. In the current study, among seventy-four isolates that showed positive results in the primary screening, four bacterial isolates demonstrated the highest activity in the secondary screening. These isolates were identified as Bacillus subtilis subsp. stercoris strain EGI18, Bacillus licheniformis strain PP1, Bacillus subtilis strain MML5328.1U, and Bacillus pumilus strain LX11, with keratinase activity values of 20.1 U/mL, 28.8 U/mL, 28.1 U/mL, and 28.1 U/mL, respectively, under standard cultivation conditions. The key nutritional and environmental parameters investigated in this study included carbon sources, nitrogen sources, pH, temperature, and inoculum size. The results showed that the optimal conditions for increasing keratinase enzyme production were: a temperature of 37°C, pH 8, glucose as the best carbon source, tryptone as the most effective nitrogen source, and an inoculum size of 1 mL. When these optimal parameters were applied in combination, maximum keratinase production was achieved from all four bacterial isolates. The keratinase activity values under optimal conditions were 139.0 U/mL for B. subtilis subsp. stercoris strain EGI18, 127.0 U/mL for B. licheniformis strain PP1, 138.0 U/mL for B. subtilis strain MML5328, and 147.0 U/mL for B. pumilus strain LX11. These findings indicate that various environmental and nutritional parameters significantly influence the production of bacterial keratinase enzymes, highlighting their importance in optimizing enzyme yield for biotechnological applications.