عنوان مقاله [English]
Introduction: Technologies commonly used for soil remediation are expensive and can lead to incomplete degradation of pollutants. Biodegradation is a cost-effective technology for the recovery of oil-contaminated areas.
Materials and methods: This study was conducted to isolate crude oil degrading bacteria, soil and sludge from 7 contaminated oil fields in Masjed Soleyman. Serial dilution and MPN methods were used to determine the frequency of heterotrophic and degrading bacterial counts. Twenty-four strains were isolated by culture enrichment in Bushnell-Haas broth medium containing half percent crude oil. Then, based on warm staining and colonial characteristics, Oil Spreading Test, Cell Surface Hydrophobicity and Emulsion Activity strains were screened for initial screening, with 10 strains as the top strains. Selected for biochemical identification. Finally, the top 10 strains were screened by spectrophotometric and gravimetric methods with a concentration of 0.5% crude oil. Also Gas Chromatography analysis were done for the best strain to confirm the crude oil degradation.
Results: 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 crude oil concentrations, nutrient effects, time effects, and mixed culture. The highest Oil Spreading was for strain (F3) and the highest Emulsion Activity was for strain (E3). D3 strain with 41% degradation at 4.5 concentration and E3 strain with 73.5% degradation at 1.5 concentration showed the best results in response to different crude oil concentrations. The results of Gas Chromatography confirmed that strain D3 can degraded 95 percent of crude oil in 0.5 % concentration.
Discussion and conclusion: The identified strains have high potential for elimination of hydrocarbon contamination and can be used at field level to reduce and eliminate oil contamination in the contaminated areas in the future.