In the current work, the biosurfactant production by three
B.subtilis strains was optimized using different carbon and nitrogen sources. The strains were found to produce biosurfactants with better surface-activities and emulsification properties when sucrose was used as carbon source. Crude biosurfactant mixtures
were found to be mainly constituted of surfactins with an heptapeptide moiety (L-Glu-L-Leu-D-Leu-L-Val-L-Asp-D-Leu-L-Leu), linked to a C13,C14 or C15 hydroxy fatty acid chain. Although several similarities were found among the biosurfactant mixtures produced by the different isolates, it was evident the presence of different variants of surfactins that could be implicated in the distinct emulsification and surface-active properties found. These biosurfactant mixtures were able to decrease the interfacial tension of
Arabian light crude oil/water system more efficiently than chemical surfactants, and showed better results in oil recovery, thus suggesting their interest for use in MEOR processes.