Isolation and identification of the same type LMG1242 of biosurfactant-producing strain of Pseudomonas aeruginosa from different oil contaminated soils

Abstract

Emulsification is a major rate limiting step in any biological conversion of heavy hydrocarbons. Here, thirty bacterial strains were isolated from seven native consortia and screened for biosurfactant-producing activities which could enhance emulsification of heavy oils. The consortia were obtained by sampling from oil contaminated soils of different petroleum refineries of Iran. The oil spreading test, drop collapse test, emulsification index (E24) and surface tension measurements were used to evaluate the biosurfactant producing activities of the strains. A total number of 5 strains out of 30 were finally selected as the best biosurfactant-producing bacteria. The clear zone diameters in their oil spreading test were 4 to 5 cm, and E24 were 48 to 92%. The selected strains also properly lowered the surface tensions of the supernatants to 23.5-32 mN/m when grown on heavy diesel. All the selected strains were identified by 16S rRNA sequencing analysis as Pseudomonas aeruginosa LMG1242 (99.9% homology) which is a newly isolated type in oil polluted soils. The results suggest P. aeruginosa LMG1242 as a predominant and highly active biosurfactant producing bacterium which could be further evaluated in petroleum bioremediation and bioprocessing applications.