Isolation and characterization of trehalose tetraester biosurfactants from a soil strain Micrococcus luteus BN56

The bacterium Micrococcus luteus BN56, isolated from soil, was found to produce glycolipid biosurfactants when grown on n-hexadecane as the sole carbon source. The purified glycolipids were characterized using 1H, 13C, 1H COSY NMR-spectroscopy and ESI-MS spectrometry analyses. The two main products were identified as trehalose tetraesters with molecular mass of 876 and 848 g mol−1. The purified products reduced the surface tension of water from 72 to 24.1 mN m−1 and the interfacial tension between water and hexadecane from 43.0 to 1.7 mN m−1. The CMC of these biosurfactants was found to be 25 mg l−1. The strain formed stable emulsions with hydrocarbon substrates and was suggested that the hydrophobic cells acted as emulsion-stabilizing agents. The results demonstrate that the strain M. luteus BN56 may be well suited for bioremediation of oil-contaminated environments.