Isolation and Characterization of Biosurfactant Producing and Crude Oil Degrading Bacteria from Oil Contaminated Soils

The aim of this work was to isolate and characterize bacteria from two crude oil-contaminated soils which were capable of producing biosurfactant and degrade oil. The contaminated soils were located in Tehran and Isfahan oil refineries, Iran. Various traits, such as hemolytic activity, oil resolving , oil spreading, and oil emulsifying capability were used to screen the isolates. Among 54 isolated isolates from two petroleum-contaminated soils, only 10 isolates were able to produce biosurfactant and degrade oil. These 10 isolates could produce glycolipid biosurfactants, which ranged from 1.93 to 3.7 g L−1. The results showed that four isolates (T4, T27, T30 and E1) could efficiently degrade crude oil in saline mineral broth, with the highest removal efficiency of 39% for T4. Gas chromatography analysis revealed that both lighter and heavier petroleum hydrocarbons were affected by microbial degradation. It was also demonstrated that branched alkanes as well as linear alkanes were degraded by the isolates. Based on 16S rDNA sequencing, all four isolates were identified as pseudomonas aeruginosa. Overall, this study shows that the biosurfactant production is a critical trait in screening of oil-degrading bacteria. Thus, the superior strains in this study are recommended for bioremediation programs, particularly in reclamation of crude oil-contaminated saline soils.