Structural Characterization of Lipopeptides from Brevibacillus brevis HOB1

Brevibacillus brevis HOB1 was isolated from the formation water of an oil field and found to produce lipopeptides. The separation of lipopeptides was successfully achieved by reversed-phase high-performance liquid chromatography (HPLC) leading to nine separated peaks. The chemical structures of these lipopeptides were studied by means of electrospray ionization mass spectrometry (ESI-MS), gas chromatography-mass spectrometry (GC/MS), HPLC and electrospray ionization tandem mass spectrometry (ESI-MS/MS). As the results, all the lipopeptides had peptide parts with the same amino acid composition of Asp, Glu, Val, and Leu in the molar ratio 1:1:1:4, while the lipid part was composed of C₁₃–C₁₅ β-hydroxy fatty acids. As the sequence of fraction 1 was determined to be N-Glu-Leu-Leu-Val-Asp-Leu-Leu-C, the same as surfactin, they were proposed to be surfactin isoforms. Fraction 4 (C₁₅ surfactin) exhibited a good surface activity of 26.8 mN/m with CMC of 9?×?10^?6 M. Surfactin is a powerful biosurfactant possessing biological activities. As far as we know, Br. brevis is a new surfactin-producing species.