Biodegradation of petrochemical industry compounds by cytochrome P450-producing toluene-degrading bacterium

Introduction: Owing to the serious environmental problems which have occurred due to the increasing amount of toxic petroleum hydrocarbons in the environment, bioremediation of these compounds by microorganisms seems to be necessary. Among these, toluene is a common pollutant in petrochemical industry and a serious cause for concern due to its adverse health effects and carcinogenic potential. Materials and methods: In this study, to isolate toluene-degrading bacteria, contaminated seawater and wastewater samples were collected from the Caspian Sea, the Persian Gulf and municipal wastewater. The best toluene-degrading bacterial strain was biochemically and molecularly characterized and its 16S rDNA sequence was submitted as Bacterium Ex-DG74 (accession no. HQ414235) in NCBI. Then, toluene removal rate, cytochrome P450 enzymatic activity, and growth rate of the isolate on oil and petrochemical contaminants were determined. Results: After enrichment procedures in toluene-containing medium, about twenty toluene-degrading bacteria were isolated. Among them, a newly isolated strain from wastewater exhibited great ability to utilize toluene as the sole source of carbon and energy. According to the results obtained by spectrophotometer and gas chromatograph, Bacterium Ex-DG74 showed a significant tolerance to organic solvent as it could grow in the medium containing %25 (v/v) toluene and also degraded over 70 of %1 (v/v) toluene as the sole source of carbon and energy. Moreover, this bacterium could grow on different toxic oil and petrochemical compounds. Discussion and conclusion: The results of the present study indicated that cytochrome P450 enzymatic activity can have essential role on biodegradation of different pollutants by Bacterium Ex-DG74. Thus, we suggest this bacterium as a potential biological agent for in situ bioremediation of hydrocarbon-polluted environments.