Fipronil is a recalcitrant phenylpyrazole-based pesticide used for flea/tick treatment and termite control that is distributed in urban aquatic environments via stormwater and contributes to stream toxicity. We discovered that fipronil is rapidly metabolized (t<sub>1/2 </sub>= 4.2 d) by the white rot fungi Trametes versicolor to fipronil sulfone and multiple previously unknown fipronil metabolites, lowering fipronil concentration by 96.5%. Using LC-QTOF-MS untargeted metabolomics, we identified four novel fipronil fungal transformation products: hydroxylated fipronil sulfone, glycosylated fipronil sulfone, and two metabolites with unresolved structures. These results are consistent with identified enzymatic detoxification pathways wherein conjugation with sugar moieties follows initial ring functionalization (hydroxylation). The proposed transformation pathway is supported by kinetic evidence of metabolite formation. Fipronil loss by sorption, hydrolysis, and photolysis was negligible. When T. versicolor was exposed to the cytochrome P450 enzyme inhibitor 1-aminobenzotriazole, oxidation of fipronil and production of hydroxylated and glycosylated metabolites significantly decreased, indicating that fipronil is metabolized intracellularly by cytochrome P450 enzymes. Elucidating fipronil transformation products is critical because pesticide target specificity can be lost via structural alteration, broadening classes of impacted organisms. Integration of fungi in engineered natural treatment systems could be a viable pesticide removal strategy for stormwater runoff.

Metabolization and degradation kinetics of the urban-use pesticide fipronil by white rot fungi <i>Trametes versicolo</i>

252nd National Meeting (2016)

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Metabolization and degradation kinetics of the urban-use pesticide fipronil by white rot fungi Trametes versicolo