Isolation and characterization of petroleum product emulsifying Pseudomonas strains from a generating set fuel tank

This study characterized microbial strains isolated from diesel fuel samples collected from the tank of a generating set at the Institute of Research for Development in Pointe-Noire (Congo). Two bacterial isolates (G2 and G3) were distinguished by their color on agar plates and were characterized by their API 20E biochemical profiles and by 16S rRNA gene sequencing. The phenotypic properties of these isolates were consistent with their assignment to the genus Pseudomonas. Comparative 16S rRNA gene sequence analysis demonstrated that the G2 and G3 isolates were close relatives of P. aeruginosa strain GIM 32 and P. aeruginosa strain NV2, respectively, with 97% sequence identity. These two P. aeruginosa strains were able to grow in a mineral salt medium supplemented with 2% diesel fuel or SAE 90 gear oil as the only source of carbon. P. aeruginosa G3 showed faster growth and was able to emulsify diesel fuel (53%), gasoline (90%) and hexane (95%) more strongly than P. aeruginosa G2.   Key words: Pseudomonas, emulsification index, diesel fuel, gasoline, hexane.