Vol. 13 No. 56-81 (2022): SCREENING OF BACTERIAL ISOLATES FROM CRUDE OIL CONTAMINATED SOIL FOR POTENTIAL TO PRODUCE BIOSURFACTANTS

Biosurfactants are heterogeneous group of surface active molecules produced by microorganisms, which adhere to cell surface or excreted extracellularly in the growth medium. This study was conducted to screen bacterial isolates from crude oil contaminated soil for potential to produce biosurfactants. Sixteen bacterial species were isolated and screened for biosurfactant production using the drop collapse test, oil displacement method and emulsification activity. Based on the screening test, nine bacterial isolates were identified as biosurfactant producing bacteria. The isolates were species of Klebsella, Micrococcus, Bacillus, Staphylococcus, Pseudomonas, Corynebacterium, Acinetobacter and Comamonas. Two efficient biosurfactant producing bacteria were confirmed by 16S rDNA sequencing as Acinetobacter baumanni strain and Comamonas testosteroni. Biosurfactants produced by the two bacteria were extracted by acid precipitation method. Acinetobacter baumanni produced 1.2g/L of biosurfactant after 7 days while Comamonas testosteroni produced 0.6g/L of biosurfactant over the same period. The biosurfactants were characterized using FTIR, GC-MS and Physicochemical content. The biosurfactant produced by Acinetobacter baumanni indicated the biosurfactant was a lipopeptide having characteristics lipid and peptide peak values, containing 35.88% protein, 18.32% lipid and 24.44% Carbohydrate, while the biosurfactant produced by Comamonas testosteroni was a glycolipid (rhamnolipid) containing 35.28%, 18.65% lipid and 26.28% Carbohydrate. This study shows that the biosurfactants produced (lipopeptide and rhamnolipid) may be useful in the management of oil spills in the environment.