Degradation of asphaltenes by two Pseudomonas aeruginosa strains and their effects on physicochemical properties of crude oil

- Two Pseudomonas aeruginosa strains were isolated from oil-contaminated soils.
- Both strains were able to degrade oil asphaltenes (59-72%) and pure asphalt (∼10%).
- Oil viscosity (35 °C) was reduced more than half by bacterial degradation.
- Quantity of vaporizable components (230 °C) increased by one fifth in degraded oil.
- The majority (90%) of oil adsorbed on filter paper was removed by P. aeruginosa.

Microbes can enhance oil recovery through the degradation of some heavy fractions of crude oil. Two Pseudomonas aeruginosa strains (Gx and Fx) using crude oil as the carbon source were isolated from oil-contaminated soils. The potential of Gx and Fx for oil displacement was assessed by testing their ability to degrade pure asphalt and crude oil asphaltenes. Approximately ∼10% of pure asphalt and 59-72% of crude oil asphaltenes were degraded using cell-containing fermentation broths. The content of lighter fractions (saturates and aromatics, maximum 11%) increased and the content of heavier fractions (resins and others, maximum 75%) decreased in the degraded oil compared with the controls. The relative quantity of vaporizable fractions (230 °C) increased after treatment, 10% by Gx and 19% by Fx. The oil viscosity (35 °C) was reduced by nearly half from 76.5 m Pa∙s, and ∼90% of oil adsorbed on filter paper was removed after treatment. Gx and Fx produced surfactants with crude oil as the sole carbon source, and the oil-spreading diameter ranged from 15 to 17 cm. In conclusion, biosurfactant-producing P. aeruginosa strains Gx and Fx could efficiently degrade recalcitrant asphaltenes in crude oil and are therefore candidate strains for microbial enhanced oil recovery.