Effects of a Biosurfactant and a Synthetic Surfactant on Phenanthrene Degradation by a Sphingomonas Strain

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 biodegradation 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.