Purification and characterization of lipopeptides produced by Bacillus subtilius and their antibacterial effects on Escherichia coli and Staphylococcus aureus

Lipopeptides have favorable biological activity and thus have great potential to serve as replacements. Whole genome sequencing was used in this work to pinpoint the gene clusters in Bacillus subtilis that code for secondary metabolites that have antibacterial qualities. Afterwards, the metabolic pathways responsible for the production of these compounds were clarified, and the lipopeptides were separated and identified using a combination of chromatography and spectroscopy methods, such as High-Performance Liquid Chromatography (HPLC), Fourier Transform Infrared Spectroscopy (FTIR), and Liquid Chromatography-Mass Spectrometry (LC-MS). Bacillus subtilis mainly synthesized surfactin homologs with carbon chain lengths ranging from C13 to C16 ([M+H]+: 994.6418; 1008.6586; 1022.6730; 1036.6896) and fengycin homologs with carbon chain lengths of C15 and C16 ([M+H]+: 1449.7937, 1463.8046). The isolated lipopeptides exhibited strong inhibitory effects against Escherichia coli and Staphylococcus aureus, with minimum inhibitory doses of 12.50 mg/L and 6.25 mg/L, respectively. Furthermore, lipopeptides demonstrated a dose-dependent inhibition of E. coli and S. aureus. The findings from SEM and SYTO 9/PI staining demonstrate that lipopeptides function by compromising the integrity of bacterial cell membranes. The results demonstrate the effectiveness of lipopeptides as antibacterial agents against foodborne pathogens, indicating their potential as substitutes for traditional antibiotics.