Biosurfactants are surface-active compounds derived from varied microbial sources including bacteria and fungi. They are secreted extracellularly and have a wide range of exciting properties for bioremediation purposes. They also have vast applications in the food and medicine industry. With an objective of isolating microorganisms for enhanced oil recovery (EOR) operations, the study involved screening of organisms from an oil-contaminated site. Morphological, biochemical, and 16S？rRNA analysis of the most promising candidate revealed it to be Bacillus siamensis, which has been associated with biosurfactant production, for the first time. Initial fermentation studies using mineral salt medium supplemented with crude oil resulted in a maximum biosurfactant yield of 0.64？g/L and reduction of surface tension to 36.1？mN/m at 96？h. Characterization studies were done using thin layer chromatography and Fourier transform infrared spectroscopy. FTIR spectra indicated the presence of carbonyl groups, alkyl bonds, and C–H and N–H stretching vibrations, typical of peptides. The extracted biosurfactant was stable at extreme temperatures, pH, and salinity. Its applicability to EOR was further verified by conducting sand pack column studies that yielded up to 60% oil recovery. 1. Introduction Biosurfactants are amphiphilic molecules which have the ability to depict a wide variety of surface activity. They comprise both a hydrophobic and a hydrophilic group that aid in its accumulation between fluid phases. Biosurfactants have the natural tendency to decrement surface and interfacial tension. Because of this property, they allow easy accessibility to nonpolar hydrocarbons so that microorganisms in oil-rich ecological niches can easily degrade them. A number of high molecular weight biosurfactants and bioemulsifiers are produced by both bacteria and fungi. Biosurfactants of bacterial origin belong to most classes of compounds including polysaccharides, proteins, lipopolysaccharides, lipoproteins and combinations of many of these structural types. Bacterial strains belonging to the genus Bacillus and Pseudomonas usually produce lipopeptide biosurfactants. Almost all classes of microorganisms (Table 1) produce biosurfactants (Finnerty [1] and Healy et al. [2]). Table 1: Examples of microbial biosurfactants. Owing to their xenobiotic nature, synthetic surfactants have the potential disadvantage of persisting in the environment, long after they are applied for a remedial measure. Also, some of the synthetic surfactants are comparatively more toxic to human health
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