This study examined the growth kinetics and antibiotic production of Bacillus sp. isolated from salted anchovy (Stolephorus sp.) wastewater, a protein-rich and saline environment. The isolate exhibited typical Bacillus characteristics: gram-positive, rod-shaped, motile, and endospore-forming, with hydrolytic enzyme activities including amylolytic, proteolytic, lipolytic, cellulolytic, and fermentative functions. Antibiotic filtrates were produced using different protein substrates skim milk, soy milk, egg yolk, and peptone under varying salinity levels (0‰, 1‰, 2‰, 5‰) with zinc supplementation. Skim milk provided the optimal nitrogen source, yielding the largest inhibition zones against Staphylococcus aureus (25 mm) and Escherichia coli (22 mm). Salinity significantly affected antibiotic activity, with 5‰ NaCl producing the highest inhibition zones of 14 mm (S. aureus) and 10 mm (E. coli). These results indicate that both the quality of nitrogen substrates and environmental salinity critically influence secondary metabolite production in Bacillus sp. The study highlights the potential of utilizing salted fish-processing wastewater as a sustainable substrate for microbial antibiotic biosynthesis, offering an eco-friendly approach to valorise industrial waste while producing bioactive compounds.
