A novel phenanthrene(PHE)-degrading strain named as Sphingomonas sp.GF2B was isolated and identified from a farmland soil.Effects of a synthetic surfactant(Tween-80)and a rhamnolipid biosurfactant on PHE degradation by Sphin-gomonas sp.GF2B were investigated at different concentrations of the surfactants.The results showed that Sphingomonas sp.GF2B was able to mineralize up to 83.6% of PHE within 10 days without addition of surfactants.The addition of Tween-80 to the reaction medium inhibited greatly PHE biodegradation,with only 33.5% of PHE degraded.However,the biosurfactant facilitated PHE biodegradation,with up to 99.5% of PHE degraded.The preferential utilization of PHE as a carbon source and the enhanced solubility of PHE by the biosurfactant were likely responsible for the higher biodegra-dation efficiency of PHE in the presence of the biosurfactant.Therefore,it could be concluded that the application of the biosurfactant to PHE-contaminated soils was perhaps a feasible way to facilitate the PHE biodegradation.