Identification and determination of individual sophorolipids in fermentation products by gradient elution high-performance liquid chromatography with evaporative light-scattering detection.

High-performance liquid chromatography (HPLC) was used for the characterization of sophorolipids, one of the most important types of glycolipid biosurfactants. By using gradient elution with a water-acetonitrile mixture on a reversed-phase (C18) column and evaporative light-scattering detection, resolution of all the important individual sophorolipids present in fermentation products was achieved. In addition to HPLC, a combination of techniques involving selective production by fermentation of sophorolipids, chemical conversions of the products, separation methods and, for identification of lipidic chains of sophorolipids, gas chromatography and mass spectrometry was used. This led to the identification of almost all significant compounds observed in HPLC, including several previously unreported sophorolipids. As a result, a rapid method is now available for investigations of the influence of fermentation conditions on the nature and quantitative distribution of the sophorolipid products obtained.