Background and Aim:Currently, Microbial degradation is the major process to remove PAH pollutants in the environment. Pyrene is one of PAH compounds, that has been used as a model to study the biological degradation of PAHs. Methods:Pyrene-degrading bacterial strains were isolated from oil-contaminated soils on the culture medium containing pyrene as sole source of carbon. The morphology and biochemical characteristic of the strains having the highest degradation in the shortest time was evaluated. Finally, D6 strain was selected for further study. This strain was identified as Achromobacter sp. by 16S rDNA gene analysis. For research purposes, five factors were studied including pH, temperature, nitrogen source and presence of glucose and NaCl to optimize pyrene degradation Results:The results demonstrated that decreasing temperature from 37 to 30 °C had a positive impact on the biodegradation of pyrene and environment pH from neutral to acidic was more favorable for the pyrene degradation. On the other hand, using of organic nitrogen source was associated with a decrease in pyrene degradation. Using (NH4)2SO4 instead of NH4NO3 stimulated pyrene bio degradation to 75% in 72 hours. Glucose did not affect on bio degradation and removal rate of pyrene was higher in the absence of NaCl. Conclusion:Results indicated that native strains have high potential to removal of pollutants and environmental condition’s optimization can be affected in shorten the removal time.

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