Effect of Rhamnolipid Biosurfactant on Solubilization and Biodegradation of Polycyclic Aromatic Hydrocarbons

The effectiveness of rhamnolipid biosurfactant on solubilization of polycyclic aromatic hydrocarbons (PAHs) in artifical seawater and biodegradation of phenanthrene by a marine bacterium Sphingobacterium sp. strain QPH-3 were investigated. Rhamnolipid above the CMC significantly enhanced the aqueous solubility of PAHs. The values of molar solubilization ratio are 4.9×10-1, 9.4×10-2, and 1.4×10-2for naphthalene, phenanthrene, and pyrene, respectively. The results of biodegradation experiments showed that the extents of phenanthrene biodegradation were significantly enhanced by rhamnolipid at the optimal concentrations. When the biodegradation systems amended with rhamnolipid dosages above 10mmol/L, the surfactant compete with PAH as substrates and therefore decrease the biodegradation rate of the phenanthrene.