biodegradation of polycyclic aromatic hydrocarbons by pseudomonas species

biodegradation of polycyclic aromatic hydrocarbons, toxic compounds widely distributed in the environment by bacteria, is a cheap and safe cleaning up method. the present study attempts to isolate and characterize dioxygenase-producing bacteria which are able to degrade phenanthrene and pyrene from refinery soils. it also aims to assess in vitro biodegradation. to do so, two contaminated soil samples were collected from isfahan-iran refinery. the population of phenanthrene and pyrene degrading bacteria were 2.17 × 103 and 1.19 × 103 cfu/g in sample 1 and  21.50 × 103 and 19.40 × 103 cfu/g in sample 2. a sum of 18 phenanthrene and pyrene degrading bacteria were isolated using enrichment culture technique, three of them getting selected which had dioxygenase activity and produced biosurfactant. identified as pseudomonas plecoglossicida atai18, pseudomonas aeruginosa atai19, and pseudomonas stutzeri atai21, they were submitted to genbank under the accession number of kf113842, kf113843, and kf113845 respectively. the degradation rate of pyrene (50 mg/l) by strains atai18 and atai19 was 45.32% and 31.23%, respectively. the strain atai21 degraded 39.38% of phenanthrene (50 mg/l) after 9 days. these isolated bacteria can be used to improve microbial population of other hydrocarbon-polluted soils for faster bioremediation of such areas.