The protease production potential of Bacillus spp. in media supplemented with fish waste as a nitrogen source

This study focuses on the valorization of fish processing waste, a major environmental issue in the seafood industry, through a biotechnological approach for the production of protease, a high value-added industrial enzyme. Nutrient-rich and low-cost fish waste was evaluated as an alternative nitrogen source to determine optimal fermentation conditions and identify the most efficient microorganism. Three bacterial strains with known protease-producing potential (Bacillus velezensis, Bacillus subtilis, and Bacillus licheniformis) were tested under different concentrations of fish waste (1–10%) and molasses (1–10%) during a 72-hour fermentation process. Extracellular protease activity was measured at 24, 48, and 72 hours using the Azocasein method, and the data were analyzed with descriptive statistics and ANOVA. The results showed that Bacillus licheniformis exhibited the highest protease production. Maximum activity of 2920.61 U/mL was achieved at 48 hours in a medium containing 2.5% fish waste and 1% molasses. ANOVA confirmed that fish waste concentration, molasses concentration, bacterial strain, and their interactions had statistically significant effects on protease production. Scale-up experiments in a bioreactor retained 92.6% of the laboratory-scale yield, demonstrating the industrial potential of the process. Overall, the findings highlight fish processing waste as a valuable raw material for sustainable industrial protease production.