Emulsification potential of a newly isolated biosurfactant-producing bacterium, Rhodococcus sp. strain TA6

An indigenous biosurfactant producing bacterium, Rhodococcus sp. strain TA6 was isolated from Iranian oil contaminated soil using an efficient enrichment and screening method. During growth on sucrose and several hydrocarbon substrates as sole carbon source, the bacterium could produce biosurfactants. As a result of biosurfactant synthesis, the surface tension of the growth medium was reduced from 68 mN m−1 to values below 30 mN m−1. The biosurfactant was capable of forming stable emulsions with various hydrocarbons ranging from pentane to light motor oil. Preliminary chemical characterization revealed that the TA6 biosurfactant consisted of extracellular lipids and glycolipids. The biosurfactant was stable during exposure to high salinity (10% NaCl), elevated temperatures (120 °C for 15 min) and within a wide pH range (4.0–10.0). The culture broth was effective in recovering up to 70% of the residual oil from oil-saturated sand packs which indicates the potential value of the biosurfactant in enhanced oil recovery.

Graphical abstract. Biosurfactant production and surface activity of newly isolated biosurfactant-producing bacterium Rhodococcus sp. strain TA6 during growth on mineral salt medium supplemented with 2% sucrose at 30 °C.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlightsA local biosurfactant producing strain identified as Rhodococcus sp. strain TA6 was isolated from soil in South of Iran. This biosurfactant has marked stability and activity in harsh conditions including extreme pH, high salinity and high temperature which are suitable properties for industrial applications. In order to determine the biosurfactant suitability and applicability in oil enhanced recovery, we have set up a lab scale sand pack test and the biosurfactant usefulness in EOR technology was confirmed. The effect of carbon source on growth and biosurfactant production by TA6 strain and the emulsification properties of the biosurfactant were also presented.