Biosurfactant production using Egyptian oil fields indigenous bacteria for microbial enhanced oil recovery

Biosurfactant production is one of the most efficient mechanisms in microbial enhanced oil recovery (MEOR) processes. This work investigates the production of biosurfactants by indigenous bacteria isolated from Egyptian oil fields, and how to optimize these produced biosurfactants for MEOR. 59 Egyptian oil reservoirs were screened to evaluate the potential applicability of MEOR processes, based on their rock and fluid properties. Results showed that 8 reservoirs from the Gulf of Suez and 3 reservoirs from the Western Desert had the potential to MEOR. Combined analysis of morphological, and biochemical characterization was performed on the 11 bacterial strains isolated from different crude oil samples collected from the reservoirs that have the potential to MEOR process to identify their types. Bacillus spp, a bacilli species that can produce biosurfactants, was selected for further studies. To optimize the surface activity of the produced biosurfactant, ten different reported nutrient media, and a new proposed nutrient media were examined. Bacillus spp has shown the ability to produce a very active biosurfactant that reduced the surface tension of water from 71.8 ± 1.9 mN/m to 25.7 ± 1.2 mN/m, and the interfacial tension of water against kerosene from 48.4 ± 2.1 mN/m to 0.38 ± 0.07 mN/m at Critical Micelle Concentration (CMC) of 0.04 ± 0.01 g/l, in a medium supplemented by the new proposed nutrient medium H. The growth rate of Bacillus spp was studied, and it was found it reached its maximum (OD600nm 2.59 ± 0.16) after 24 h of incubation. Biosurfactant production has no significant change in its surface activity over a wide range of temperature range up to 120 °C, which means the studied species Bacillus spp is a thermophilic bacterium. Bacillus spp grew well in the presence of high salt concentration up to 20% (w/v) NaCl, the optimal surface activity was obtained in the range of 0–2% (w/v) NaCl, and at pH 7. The emulsification activity of the produced biosurfactant was examined, and it reached the maximum (69.6 ± 1.5%) against kerosene at temperature 25 °C, Salinity 0% (w/v) NaCl (distilled water), and pH 7. The produced biosurfactant was purified and extracted by acid precipitation method, and the biosurfactant yield of the purified compound was found to be 2.8 ± 0.3 g/l. Finally, the core-flooding experiments were conducted to investigate the effect of produced biosurfactants by Bacillus subtilis in oil recovery. The obtained results reveal the potential of Bacillus spp to grow in the new proposed medium H and produce effective and efficient biosurfactants that enhanced oil recovery by 25.19–39.35% of additional oil over the water flooding residual oil saturation in the studied cores and retain more than 60% of its surface activity under harsh conditions and that are relevant to Microbial Enhanced Oil Recovery, MEOR.