Nonionic surfactants induced changes in cell characteristics and phenanthrene degradation ability of Sphingomonas sp. GY2B

• Biodegradation of phenanthrene was stimulated by Tween80.
• Triton X-100 slightly inhibited phenanthrene biodegradation.
• Brij30 exhibited severely inhibitory effects on phenanthrene biodegradation.
• Modification of cell vitality was the vital factor in phenanthrene biodegradation.
• Flow cytometry was used to identify cell vitality at a single cell level.

Surfactant-mediated bioremediation has been widely applied in decontaminating PAH-polluted sites. However, the impacts of surfactants on the biodegradation of PAHs have been controversial in the past years. To gain a clear insight into the influencing mechanisms, three nonionic surfactants (Tween80, TritonX-100 and Brij30) were selected to systematically investigate their effects on cell surface properties (membrane permeability, functional groups and elements), cell vitality as well as subsequent phenanthrene degradation ability of Sphingomonas sp. GY2B. Results showed that biodegradation of phenanthrene was stimulated by Tween80, slightly inhibited by TritonX-100 and severely inhibited by Brij30, respectively. Positive effect of Tween80 may arise from its role as the additional carbon source for GY2B to increase bacterial growth and activity, as demonstrated by the increasing viable cells in Tween80 amended degradation systems determined by flow cytometry. Although TritonX-100 could inhibit bacterial growth and disrupt cell membrane, its adverse impacts on microbial cells were weaker than Brij30, which may result in its weaker inhibitive extent. Results from this study can provide a rational basis on selecting surfactants for enhancing bioremediation of PAHs.