Production of Rhamnolipids by Pseudomonas aeruginosa HB6 (39) Isolated from Petroleum-Hydrocarbon Contaminated Environment

The current study evaluated hydrocarbon-degrading and biosurfactant-producing potentials of bacteria isolated from hydrocarbon contaminated soil in Nigeria, the largest crude oil reservoir in Africa. Pure bacterial isolates were grown on nutrient and Bushnell Haas agar. Bacterial isolates that grew on both media were molecularly identified via 16S rDNA sequence. Biosurfactant production detection was carried out via oil spread test, drop collapse test and surface tension measurement. The bacterial isolate with the lowest surface tension value was used for further studies. The growth of the selected isolate was measured using Spectroscopic technique, while the production of biosurfactants in the culture supernatant were determined by the measurement of surface tension, and the extracted surfactants were characterized by High Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS). The colony forming unit on nutrient agar ranged from 1.35 x 108 to 1.93 x 108 cfu/g while the colony forming unit on Bushnell Haas agar ranged from 9.33 x 105 to 1.84 x 106 cfu/g. The bacterial species belonged to three genera including Bacillus, Cellulosimicrobium and Pseudomonas. P. aeruginosa HB6 (39) with accession number MW367569.1 had the lowest surface tension value (33.77±0.12a) indicating that it was the best biosurfactant producer. The test isolate attained early stationary phase at 10h and the cell-free supernatant showed excellent surface tension reduction potential. The extracted biosurfactant contained ample mono and di-rhamnolipid congeners. P. aeruginosa HB6 (39) is a potential bioremediation agent and can also be used for large scale production of rhamnolipids for other industrial applications.