Marine bacterium derived lipopeptides: characterization and cytotoxic activity against cancer cell lines

Abstract

A marine Bacillus circulans DMS-2 was able to grow and produce biosurfactant on Glucose Mineral Salts Medium (GMSM) with a reduction in the surface tension up to 27 mN m⁻¹. The microorganism produced 1.64 ± 0.1 g l⁻¹ of crude biosurfactant. The lipopeptide nature of the produced biosurfactant was confirmed by primulin and ninhydrin assays using High Performance Thin Layer Chromatography (HPTLC). Preparative Thin Layer Chromatography (TLC) was performed to purify the lipopeptides from the crude biosurfactant. The Critical Micelle Concentrations (CMC) of the crude and purified products were found to be 90 and 40 mg l⁻¹ respectively. Fourier Transform Infrared spectrophotometer (FTIR) and Matrix Assisted Laser Desorption/Ionization Time of Flight (MALDI-ToF) mass spectral analysis revealed the identity of the produced lipopeptides as surfactin (m/z 1,023 Da) and fengycin (m/z 1,495 Da) isoforms. The purified marine lipopeptides displayed a significant antiproliferative activity against the human colon cancer cell lines HCT-15 (IC₅₀ 80 μg ml⁻¹) and HT-29 (IC₅₀ 120 μg ml⁻¹).