Isolation and Identification of Crude Oil Degrading Bacteria from Oil-polluted Areas in Masjed Soleyman

Today, one of the main environmental problems is hydrocarbon pollution due to the activities of oil and petrochemical industries. Accidental oil spills occur in the environment during the exploration, production, transportation, and storage of petroleum products. Technologies commonly used for soil remediation are expensive and can lead to the incomplete degradation of pollutants. Biodegradation is a cost-effective technology for the recovery of oil-contaminated areas.

This study was conducted to isolate crude oil degrading bacteria, soil, and sludge from seven oil-contaminated areas in Masjed Soleyman. To determine the frequency of heterotrophic and degrading bacteria, the bacteria were counted by the serial dilution and MPN methods. Twenty-four strains were isolated by the culture enrichment method in Bushnell-Haas broth medium containing 0.5% crude oil. Then, based on warm staining and colonial characteristics, oil spreading test, cell surface hydrophobicity, and the emulsion activity of the strains were examined for initial screening. Finally, the top 10 strains were screened by spectrophotometric and gravimetric methods with a concentration of 0.5% crude oil. Also, Gas Chromatography (GC) was performed on the superior strain.

The identified strains belonged to the genus Rhodococcus jostii strain D3 and Arthrobacter citreus strain E3. The top two strains were studied to investigate the effects of different concentrations of crude oil, nutrient effects, time effects, and mixed culture. The highest oil expansion was related to F3 strain and the highest emulsion activity rate was related to E3 strain. D3 strain with 41% degradation at the concentration of 4.5 and E3 strain with 73.5% degradation at the concentration of 1.5 showed the best results in response to different crude oil concentrations. The results of gas chromatography analysis confirmed that strain D3 can degrade 95 percent of crude oil at the concentration of 0.5%.

The identified strains have a great potential in removing hydrocarbon pollution and can be used at the field level to reduce and eliminate oil pollution in the contaminated areas in the future.