Isolation and identification of biosurfactant producing and crude oil degrading Pseudomonas aeruginosa strains

Petroleum hydrocarbons such as crude oil are important environmental contaminants. This study aims to isolate and identify bacterial strains from crude-oil contaminated environments with the capacity to produce biosurfactants when grown on a hydrophobic phase as well as to degrade petroleum hydrocarbons. Three strains were screened out using a combination of blood nutrient agar (NA) plate screening and crude oil mineral salt medium (MSM) plate tests. Grown on waste frying oil, all three strains were shown to produce rhamnolipids as biosurfactants. The three strains could also degrade n-alkanes up to n-C-40. The removal efficiency of crude oil of each strain after 7 days of aerobic cultivation ranged from 36.0% to 46.4%, among which strain Z41 performed best. Gas chromatographic analysis of the residual oil showed that the degradation characteristics of the three strains differed from each other. The three strains behaved similarly in terms of glycolipid production as in crude oil degradation, suggesting biosurfactant production played a vital role in petroleum degradation. Using morphological, biochemical and physiological characterization and 16S rRNA sequencing, the three strains were identified as Pseudomonas aeruginosa, however producing very little amounts of pyocyanin. In this study, an efficient and simple protocol to screen out biosurfactant producing and crude oil degrading bacterial stains was developed. The reason why P. aeruginosa is often employed as biosurfactant-producing or oil-degrading strain may be found in its wide spread occurrence in contaminated environments, rapid growth, the ease of isolation and screening as well as the high biosurfactant production and crude oil degradation capacity. (C) 2012 Elsevier B.V. All rights reserved.