Improved production, purification and characterization of biosurfactants produced by Serratia marcescens SM3 and its isogenic SMRG-5 strain.

In this study, the biosurfactants (Bs) production of two Serratia marcescens strains (SM3 and its isogenic SMRG-5 strain) was improved and the tenso-active agents were purified and characterized. A 2(3) factorial design was used to evaluate the effect of nitrogen and carbon sources on the surface tension (ST) reduction and emulsion index (EI24) of the produced Bs. Optimum Bs production by SM3 was achieved at high concentrations of carbon and nitrogen, reducing ST to 26.5 +/- 0.28 dynes/cm, with an EI24 of 79.9 +/- 0.2%. Meanwhile, the best results for SMRG-5 were obtained at low concentrations, reducing the ST to 25.2 +/- 0.2 dynes/cm, with an EI24 of 89.7 +/- 0.28%. The optimal conditions for Bs production were scaled up in a 2-L reactor, yielding 4.8 and 5.2g/L for SM3 and SMRG-5, respectively. Gas Chromatography-Mass Spectrometry (GC-MS) analysis revealed the presence of two different lipopeptides (hidrofobic fractions: octadecanoic and hexadecanoic acid for SM3 and SMRG5, respectively). Both strains were capable of benzo [a] pyrene removal (59% after 72H of culture).