Biodegradation of mono-, di- and trifluoroacetate by microbial cultures with different origins

Abstract

This work focused on the biodegradation of three structurally related fluoroacetates (FAs), mono- (MFA), di- (DFA) and trifluoroacetate (TFA), using as microbial inocula samples collected from a site with a long history of industrial contamination and activated sludge obtained from a municipal wastewater treatment plant. Biodegradation experiments were carried out under different modes of substrate supplementation, which included (i) FAs fed as sole carbon sources; (ii) FAs (only for DFA and TFA) fed in co-metabolism with sodium acetate; and (iii) mixtures of MFA with DFA or TFA. Biodegradation of the target compounds was assessed through fluoride ion release. Defluorination was obtained in the cultures fed with MFA, while DFA and TFA were recalcitrant in all tested conditions. When present in mixture, DFA was shown to inhibit biodegradation of MFA, while TFA had no effect. A total of 13 bacterial isolates obtained from MFA degrading cultures were found to degrade 20mgL of this compound, as single strains, when supplemented as a sole carbon source. Sequencing of the 16S rRNA gene indicated that among these degrading bacteria only Delftia acidovorans had been previously reported to be able to degrade MFA. This work shows that, despite their similar chemical structures, biodegradation of the three tested FAs is very distinct and draws attention to the unknown impacts that the accumulation of DFA and TFA may have in the environment as a result of their high recalcitrance.

Evidence for the Formation of Difluoroacetic Acid in Chlorofluorocarbon-Contaminated Ground Water

“…On the other hand, the abiotic degradation of TFA in water is very slow [20]. The relevance of the reported anaerobic microbial degradation of TFA in laboratory experiments [9,21] for the environmental fate of TFA is not fully clarified [22], and does support reductive defluorination as an alternative source of DFA formation.…”

Combining Culture-Dependent and Independent Approaches for the Optimization of Epoxiconazole and Fludioxonil-Degrading Bacterial Consortia

“…For all bacterial formulations, similar cellular densities of each strain were used (optical densities at 600 nm of 0.20 ± 0.05). Each bacterial combination and respective control culture were inoculated in duplicate into 100 mL borosilicate flasks containing 30 mL of a sterile minimal salts medium (MM) [ 13 ] and supplemented with 5 mg·L −1 of the target fungicide (each compound dissolved in a 0.1% v / v methanolic solution). Following previously optimized conditions [ 7 ], these cultures were also fed twice a week with 400 mg·L −1 of sodium acetate and incubated in closed flasks for 28 days at room temperature, in static conditions and protected from light.…”

“…Cellular optical densities were determined by spectrophotometry, by reading the absorbance of culture aliquots at 600 nm in a V-1200 spectrophotometer (VWR International, LLC, Philadelphia, PA, USA). Defluorination of the target pesticides was used as a biodegradation indicator and was determined through potentiometric quantification of the fluoride anion in the cultures supernatants, as described in Alexandrino et al [ 13 ].…”

Why Is the Biodegradation of Polyfluorinated Compounds So Rare?

“…A notable exception is the fluorinated natural product monofluoroacetate, which is produced by both plants and microbes ( 12 ). Perhaps it is then not surprising that many genera of bacteria have been shown to defluorinate monofluoroacetate ( 14 , 15 ).…”