Tolerance and cytotoxicity of naphthenic acids on microorganisms isolated from oil sands process-affected water

The expansion of oil sands has made remediation of oil sands process-affected water (OSPW) critical. As naphthenic acids (NAs) are the primary contributors to toxicity, remediation is required. Bioremediation by native microorganisms is potentially effective, however, toxicity of NAs towards native microorganisms is poorly understood. The aim of this study was to isolate microorganisms from OSPW, assess tolerance to stressors, including naturally sourced NAs and examine exposure effect of NAs on cell membranes. Microorganisms were isolated from OSPW, including the first reported isolation of a fungus (Trichoderma harzianum) and yeast (Rhodotorula mucilaginosa). Isolates tolerated alkaline pH, high salinity, and NA concentrations far exceeding those typical of OSPW indicating toxic effects of OSPW are likely the result of interactions between OSPW components. Comparisons of toxicity determined that OSPW exhibited higher cytotoxicity than NAs. The fungal isolate was able to grow using commercial NAs as its sole carbon source, indicating high resistance to NAs' cytotoxic effects. Future studies will focus on the organisms' ability to degrade NAs, and subsequent effects on toxicity. Characterization of OSPW constituents should be investigated with focus on the synergistic toxic effects of dissolved compounds. A better understanding of OSPW toxicity would enable more effective and targeted bioremediation schemes by native microorganisms.