The maximum biosurfactant synthesis (4.97 g/L)
occurred at 96 h when the cells were grown on modified PPGAS medium containing 1% (v/v) molasses
at 30 ◦C and 150 rpm. The cell free broth containing the biosurfactant could reduce the surface tension
to 30.14 mN/m. The surface active compound showed emulsifying activity against a variety of
hydrocarbons and achieved a maximum emulsion index of 84% for sunflower oil. Compositional analysis
of the biosurfactant reveals that the extracted biosurfactant was a glycolipid type, which was
composed of high percentages of lipid (∼65%, w/w) and carbohydrate (∼32%, w/w). Fourier transform
infrared (FT-IR) spectrum of extracted biosurfactant indicates the presence of carboxyl, hydroxyl and
methoxyl functional groups. The mass spectra (MS) shows that dirhamnolipid (l-rhamnopyranosyll-
rhamnopyranosyl-3-hydroxydecanoyl-3-hydroxydecanoate, Rha-Rha-C10-C10) was detected in abundance
with the predominant congener monorhamnolipid (l-rhamnopyranosyl--hydroxydecanoyl-
-hydroxydecanoate, Rha-C10-C10). The crude oil recovery studies using the biosurfactant produced
by Pseudomonas sp. 2B suggested its potential application in microbial enhanced oil recovery and
bioremediation.
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