Despite recent efforts to introduce renewable energy sources to the market, the world still relies heavily on crude oil and petroleum-based products. It is estimated that over two-thirds of the crude in an oil reservoir remains untouched. Primary oil recovery, the process through which simple drilling and pressure differences allows gushing oil to be captured, harvests only 5–10% of the original oil in place. Several enhanced oil recovery processes are currently employed worldwide: thermal, chemical, physical, etc. However, these processes are very expensive as well as environmentally harmful. Thus, the search for alternative, cost-effective, eco-friendly alternatives to the chemical and thermal enhanced oil recovery methods is necessary. MEOR consists of the tertiary recovery of oil in which microorganisms or their metabolic products are used to recover residual oil. Microorganisms produce polymers and biosurfactants, which reduce oil-rock surface tension by diminishing the capillary forces that impede the movement of oil through the pores of rock.
Since long term exposure to petroleum hydrocarbons would be expected to select for the development of biosurfactant-producing bacteria via horizontal gene transfer and metabolic switching, chronically contaminated sites should contain bacteria that produce effective surfactants that can be used by many different petroleum-degrading species that are indigenous to petroleum-dominated habitats. Microbial consortium isolated from creosote tar contaminated soil revealed a significant production of biosurfactant with important emulsification and surface tension reduction activities during growth on sunflower oil (2%, v/v). After, 6 days of growth of the microbial consortium on oil supplemented with mineral salt medium the biosurfactant produced was recovered. The biosurfactant produced by the consortium showed enhanced oil recovery performance compared to distilled water control. The biosurfactant (cell free supernatant) showed an 88% oil recovery from spiked sand in 48 hours compared to 26% with distilled water. The results suggested the potential application of the biosurfactant produced by the microbial consortium for enhanced oil recovery and other related applications in petroleum industry.