Genome mining, structural elucidation and surface-active property of a new lipopeptide from Bacillus subtilis

The Bacillus genus is well known for producing structurally diverse lipopeptides, many of which exhibit remarkable surface-active and bioactive properties, such as surfactin and daptomycin. In recent years, genome mining has emerged as an effective tool for the discovery of novel natural products by predicting biosynthetic gene clusters and linking them to secondary metabolite production. However, the full biosynthetic potential of many Bacillus subtilis strains remains unexplored. Therefore, this study aimed to investigate the biosynthetic potential of an oilfield-isolated Bacillus subtilis strain through genome mining, with the goal of identifying novel lipopeptides with enhanced surface activity.

In this study, we identified 14 biosynthetic gene clusters, four of which were related to lipopeptide biosynthesis. In addition, a lipopeptide was characterized as a new member of the surfactin family, namely surfactin-C18. The primary structure of surfactin-C18 was determined to be a heptapeptide ring of N-Glu-Leu-Leu-Val-Asp-Leu-Leu-C linked to the longest β-hydroxy fatty acid in the surfactin family, containing 18 carbon atoms. Moreover, we investigated the surface activity of surfactin-C18, measuring its critical micelle concentration and the surface tension to be 1.99 µmol/L and 28.63 mN/m, respectively. The obtained adsorption parameters of surfactin-C18 at the air/liquid interface further explained its enhanced surface activity in comparison with other surfactin homologs and commercial surfactants.

To the best of our knowledge, this is the first report on the structural characterization and surface activity of surfactin-C18. In addition, our findings not only demonstrate the biosynthetic potential of B. subtilis but also highlight the power of the genome mining strategy for discovering novel lipopeptides with industrial applications.