Background & Objectives: Environmental pollution by oil and its derivatives is a serious threat to human health and the environment. Therefore, treatment of these compounds is important. In order to achieve high biodegradation efficiency, isolation of efficient bacteria as well as identifying optimal biodegradation conditions are important. The aims of the study were to isolate and identify crude oil degrading strain from surface sediments of Arvandkenar region, identifying optimal biodegradation conditions as well as evaluating degradation of different fraction of synthetic and crude oil by isolated strain.

Methods: Surface sediment samples of Arvandkenar were collected. Isolated strains were identified after enrichment of crude oil degrading bacteria in a mineral salt medium. The NH₄Cl and K₂HPO₄ concentrations were optimized to achieve the best conditions for crude oil biodegradation by isolated strain. The ability of bacterial isolate to degrade different fractions of oil was studied gravimetrically. The ability of the isolated strain to degrade hexadecane, dibenzothiophene, naphthalene, phenanthrene and pyrene was studied using Gas chromatography.

Results: Among the isolated strains, BN₂ had the highest efficiency and showed 99% similarity to Pseudomonas aeruginosa. BN₂ strain had the optimum function at 0.25 and 0.024g/l of NH₄Cl and K₂HPO₄, respectively and removed >80% of oil within 5 days. The results of gravimetric analysis showed isolated strain to degrade aliphatic, aromatic, resin and asphaltenes with the highest removal rate belonging to naphthalene.

Conclusions: Indigenous bacteria from surface sediments of Arvandkenar degrade crude oil. Due to high biodegradation ability of BN₂, they can be used for bioremediation of petroleum contaminated soil in the Arvandkenar region.