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Characterization and oil recovery application of biosurfactant produced during bioremediation of waste engine oil by strain Pseudomonas aeruginosa gi|KP 16392| isolated from Sambhar salt lake

Abstract Halophilic bacterium, Pseudomonas aeruginosa gi|KP 16392| isolated from Sambhar salt lake in the southwest region of the city of Jaipur, India was tested for the first time for potential application in waste engine oil bioremediation and simultaneous biosurfactant production. In this study, the batch experiments were performed on culture grown in mineral salt medium supplemented with 5% (v/v) waste engine oil as the sole carbon source incubated for a week at pH 7.0, maintaining 35 °C and 150 rpm. The bacterial growth was monitored by the optical density and dry biomass content measurements. The biosurfactant production was affirmed with the reduction in surface tension of the culture medium from 72 ± 0.36 to 29.61 ± 0.14 mN/m. Of the total waste engine oil fed, 74.35 ± 0.037% was consumed and biodegraded to secondary metabolites. The biosurfactant yield was found to be approximately 1.02 g/L. The functional groups in the product, identified with the Fourier transform infrared spectroscopy confirms to be rhamnolipid and characterized using microbial adhesion to hydrocarbon (math) test and methyl assay. The emulsification activity of the produced biosurfactant was assessed for various hydrophobic substrates and was found to be comparable to the chemical surfactant (sodium dodecyl sulfate). The biosynthetic pathway (de novo synthesis) used by microbial strain to form rhamnolipid is schematically represented. The performance of the purified biosurfactant in oil recovery application was tested using a simulated waste engine oil contaminated soil and it showed excellent surface activity.