Functional Evaluation and Physicochemical Characterization of a Lipopeptide Biosurfactant Produced by the Stenotrophomonas sp. IE-93

In the present work, biosurfactant production of the bacterial strain Stenotrophomonas sp. IE-93 was surveyed and quantified through four conventional screening methods. The biosurfactant produced by the strain IE-93 could reduce the surface tension to 24mNm(-1) and showed 100% emulsification activity when equal volume of n-hexane and fermentation medium was applied. Effects of culture conditions on productivity of the strain revealed that olive oil and ammonium sulfate were the best carbon and nitrogen sources, respectively. The crude produced biosurfactant showed a good stability during exposure to high temperatures (up to 120 degrees C), high salinity (up to 20% NaCl) and a wide range of pHs (2.0-12.0). Purification of the biosurfactant was performed using ethyl acetate, and crude extract was separated on silica gel column chromatography. The chemical characterization of the purified biosurfactant by FTIR spectroscopy revealed that it has a lipopeptide nature. Moreover, ultraviolet mutation of Stenotrophomonas sp. IE-93 yielded a stable mutant that produced over 1.7-fold more of the biosurfactant than the parent strain. Overall, the results suggest that Stenotrophomonas sp. IE-93 could be suitable candidate to use in various industrial processes needing emulsifier, especially in oil industry which needs a stable surfactant in high temperature and salinity conditions.