Optimization Strategy of Polycyclic Aromatic Hydrocarbon Contaminated Media Bioremediation through Biosurfactant Addition

A microbial surfactant was investigated for its potential to enhance bioavailability and, hence, the biodegradation of PAHs contaminated soil. Phenanthrene, a 3-ring polycyclic aromatic hydrocarbon (PAH), was chosen as a model target compound. The bioavailability and biodegradation tests were performed in aqueous and soil-slurry microscosms. The rhamnolipid biosurfactant used in this study was extracted from culture supernatants after growth of Pseudomonas aeruginosa BP9 strain in nitrogen-limited mineral salts medium. Solubilisation of phenanthrene in aqueous solution was enhanced by 400 mg of the rhamnolipid per litre increasing more than 19 folds. Phenanthrene aqueous phase biodegradation experiments were done with an initial concentration of 200 mg/L and showed 92 % mineralization in 6 days with a rhamnolipid concentration of 400 mg/L, in comparison to the 27 % mineralization of the other microcosm with no rhamnolipid amendment. Which accelerated the biodegradation rate, by increasing the bioavailabilty and by shortening the lag phase. This shows the potential application of the rhamnolipid in stimulating in-situ and ex-situ enhanced bioremediation of polycyclic aromatic hydrocarbon contaminated media.