Biodefluorination and biotransformation of fluorotelomer alcohols by two alkane‐degrading Pseudomonas strains

Abstract

Fluorotelomer alcohols [FTOHs, F(CF(2))(n) CH(2)CH(2)OH, n = 4, 6, and 8] are emerging environmental contaminants. Biotransformation of FTOHs by mixed bacterial cultures has been reported; however, little is known about the microorganisms responsible for the biotransformation. Here we reported biotransformation of FTOHs by two well-studied Pseudomonas strains: Pseudomonas butanovora (butane oxidizer) and Pseudomonas oleovorans (octane oxidizer). Both strains could defluorinate 4:2, 6:2, and 8:2 FTOHs, with a higher degree of defluorination for 4:2 FTOH. According to the identified metabolites, P. oleovorans transformed FTOHs via two pathways I and II. The pathway I led to the production of x:2 ketone [dominant metabolite, F(CF(2))(x)C(O)CH(3); x = n - 1, n = 6 or 8], x:2 sFTOH [F(CF(2))(x)CH(OH)CH(3)], and perfluorinated carboxylic acids (PFCAs, perfluorohexanoic, or perfluorooctanoic acid). The pathway II resulted in the formation of x:3 polyfluorinated acid [F(CF(2))(x) C(2)CH(2) COOH] and relatively minor shorter-chain PFCAs (perfluorobutyric or perfluorohexanoic acid). Conversely, P. butanovora transformed FTOHs by using the pathway I, leading to the production of x:2 ketone, x:2 sFTOH, and PFCAs. This is the first study to show that individual bacterium can bio-transform FTOHs via different or preferred transformation pathways to remove multiple --CF(2) -- groups from FTOHs to form shorter-chain PFCAs.

Aerobic Soil Biotransformation of 6:2 Fluorotelomer Iodide

“…19 6:2 FTOH soil biotransformation pathways were described in detail 19 and were later confirmed by pure Pseudomonas bacterial culture. 41 In this study, PFPeA and 5:3 acid were observed as two abundant products, consistent with a previous soil biotransformation study with 6:2 FTOH 19 and further confirming that the 6:2 FTOH route was operational in soil dosed with 6:2 FTI. However, PFBA was not observed, and the PFHxA level was less than half of that in soil dosed with 6:2 FTOH ( Table 1), suggesting that part of the 6:2 FTOH route may have been diverted toward the putative 6:2 FTUI route in soil dosed with 6:2 FTI, producing significant amounts of PFHpA.…”

Methodology for studying biotransformation of polyfluoroalkyl precursors in the environment

“…For a test system with simple components and weak matrix interference, such as a pure bacterial culture, a straightforward water-miscible solvent extraction (WMSE) plus centrifugation and filtration procedures would be sufficient to obtain a representative sample extract for further instrumental analysis [31]. This was done by adding an equal or slightly larger volume of a solvent (e.g., acetonitrile) to the bacterial liquid culture medium to extract precursors and transformation products.…”

“…Soil is the primary deposit medium of volatile precursors through atmospheric deposition, while sewage sludge and river sediment are important sinks of PFASs in aqueous systems from household and industry emissions [15][16][17]. To obtain knowledge on the specific microorganisms responsible for the polyfluoroalkyl precursor biotransformation processes, microbial consortium or pure bacterial cultures from soil and sewage sludge were isolated and used [30][31][32]. To elucidate the metabolism mechanism and possible adverse effects due to covalent binding of unsaturated polyfluoroalkyl intermediate metabolites to biological macromolecules, in-vitro bioassays were performed using hepatocytes, cytosol fractions and liver microsomes from mammalian and fish species [19,21].…”

Aerobic Biotransformation of Fluorotelomer Thioether Amido Sulfonate (Lodyne) in AFFF-Amended Microcosms

“…For example, Wang et al (2011) detected PFBA formation (accounting for approximately 0.14% mol/mol) when 6:2 FtS was aerobically oxidized, 24 whereas production of PFBA was also observed when 6:2 FtOH was biotransformed under aerobic conditions. 23,25,26 In this study, PFBA accounted for approximately 0.1% (mol/mol) of the total amended 6:2 FtTAoS at the end of the incubation. It is possible that 8:2 FtS biotransformation also produced the C n−2 PFCA product, PFHxA, as aerobic 8:2 FtOH biotransformation to PFHxA has been previously observed.…”