An Economical Bioprocess for Lipopeptide Production From Bacillus subtilis.

Phytopathogenic fungi such as Fusarium solani (F. solani), Rhizoctonia solani (R. solani), and Botrytis cinerea (B. cinerea) cause plant diseases, leading to significant yield losses. Lipopeptides (LPs), secondary metabolites produced by Bacillus strains, exhibit antifungal properties against these pathogens. In this study, the LP production potential of Bacillus isolates was investigated, and the best-performing Bacillus sp. was selected for the optimization of the production medium and parameters. Hemolytic activities of Bacillus isolates were screened using blood agar, revealing that all 69 isolates exhibited hemolytic activity. The isolates were cultivated in Lysogeny Broth (LB) medium, and LP extractions were performed. The antifungal activity of LP extracts against F. solani, R. solani, and B. cinerea was assessed using the agar well diffusion method. The iturin and surfactin content of LP extracts was analyzed by quadrupole time-of-flight mass spectrometry. Five Bacillus sp. with high LP production potential were selected, and their cell growth was examined. Among them, Bacillus subtilis 4-Ka-22 demonstrated the highest cell growth. The cost-effective optimized production medium was determined as 0.1% molasses, 1% soybean meal, 0.5% CaCl2, and 1% glycerol, with production parameters set at 30°C, 195 rpm, pH 5, and a 4.3% inoculum ratio. Compared to LB medium, cell growth increased by 13.4-fold, confirming successful optimization.