TFA-defluorinating microbial consortium achieved with analogue enrichment

Abstract

Trifluoroacetate (TFA) is an ultra-short chain perfluoroalkyl substance (PFAS) and a pollutant of global significance; it is persistent and ubiquitous in the environment across compartments, including food, drinking water, animals, and humans. Concentrations in the environment are rising, concerns over the toxicity of the compound are increasing, and there are currently no efficient ways to remediate TFA pollution, as conventional methods are ineffective at scale under environmental conditions. Microorganisms possessing dehalogenating enzymes targeting the structurally analogous compound monofluoroacetate (MFA) present a potential solution to degrade TFA microbiologically. Due to previously demonstrated dehalogenation of difluoroacetate (DFA) by dehalogenases, the promiscuity of such enzymes was hypothesized to be extendable to TFA as well. In this study cultures obtained from an environmental sample of PFAS contaminated wastewater sludge were incubated in M9 minimal media supplied with 33 mM acetate and either 33 mM TFA, DFA, or MFA in an iterative manner, followed by testing in a 30-day experiment. Free fluoride (F-) was measured at 5 timepoints using a fluoride ion specific electrode (ISE). One culture designated MFA1C significantly degraded MFA, DFA, and TFA (two-way ANOVA mixed model, p < 0.05). MFA1C released 11.2 {+/-} 0.7 M F- which constitutes approximately 0.01% of the potential fluoride release from the total 33 mM TFA applied and with the greatest defluorination activity in the first 9 days of incubation. Fluoride release from TFA and formation of DFA and MFA was confirmed with 19F-NMR. Genetic sequencing and protein-ligand modelling identified two candidate dehalogenase enzymes from Achromobacter denitrificans and Stenotrophomonas sp., respectively, with potential capacity to degrade TFA. The findings of this study are a crucial first step towards future potential bioremediation of TFA, and are, to the best of our knowledge, the first to identify a TFA-degrading consortium of microorganisms.