Evaluation of Biodegradation of Petroleum Aromatic Compounds with Soil Microorganisms in Tabriz City

Oil contaminated soils usually harbor bacterial species capable of degrading aromatic compounds. Polycyclic aromatic hydrocarbons (PAHs) such as anthracene, naphthalene, phenanthrene, are the most toxic and carcinogenic pollutants which cause severe damages to the environment and living organisms. These compounds are mainly discharged to the soil by petrochemical industries. Biological methods by using efficient microorganisms isolated from oil contaminated soils are preferred for removing these materials from soils. The microorganisms use hydrocarbons as sources of carbon and energy to produce water, CO2, biomass and harmless materials. In this study, soil samples were taken from different oil-pollute regions of the Tabriz Petroleum Refinery, Petrochemical Industry, gasoline service stations and cargarages. The soil suspensions were cultured in selective media and 100 isolates were obtained. Phenanthren, anthracene and naphthalene at a rate of 1000 mg/L were added to the Muller Hilton broth medium and then a fixed amounts of these bacteria were added, separately. They were incubated in shaker-incubator with 130 rpm at 28˚C for one week. The rate of PAHs destruction was evaluated by spectrophotometery method. Many bacterial isolates possessing different PAHs destroying rates were obtained. Among the isolates, %51, %47 and %41 of them were capable of destruction(up to %30) of naphthalene, anthracene and phenanthrene, respectively. By improving the growth conditions and proliferation of effective bacteria it can be possible to remediate PAHs- polluted soils in oil contaminated regions.