Hyperthermophilic Clostridium Sp. N-4 Produced a Glycoprotein Biosurfactant That Enhanced Recovery of Residual Oil at 96 °C in Lab Studies

Biosurfactant producing hypethermophilic microorganisms are essentially required for Microbial Enhanced Oil Recovery (MEOR) from high temperature oil reservoirs (above 90 degrees C). In the present study, biosurfactant producing Clostridium sp. N-4, optimally growing at 96 degrees C was isolated from a high temperature oil reservoir. Effect of pH, temperature and salinity on production and activity of N-4 biosurfactant was investigated. Biosurfactant produced by N-4 was partially purified by acid precipitation, characterized using FT-IR spectroscopy; and evaluated for its ability to enhance oil recovery in sand pack studies. The strain N-4 produced biosurfactant over a wide range of pH (5.0-9.0) and salinity (0-13%) at high temperature (80-100 degrees C) and optimally at pH 7, 96 degrees C and 4% salinity. N-4 biosurfactant was active at 37-101 degrees C; pH, 5-10 and salinity of 0-12 % (w/v). N-4 biosurfactant, characterized as glycoprotein reduced the surface tension of water by 32 +/- 0.4 mN/m at critical micelle concentration of 100 mu g/ml. N-4 biosurfactant mobilized 17.15% of residual oil saturation in sand pack studies. Similarly, the strain N-4 also recovered 36.92% of the residual oil in sand pack studies under the conditions mimicking the environment of depleted high temperature oil reservoir. Thus, the biosurfactant producing Clostridium sp. N-4 was identified as a suitable agent for enhanced oil recovery from high temperature oil reservoirs.