title: 5:3 Polyfluorinated acid aerobic biotransformation in activated sludge via novel "one-carbon removal pathways".
abstract: The polyfluorinated carboxylic acids 5:3 acid (C(5)F(11)CH(2)CH(2)CO(2)H) and 7:3 acid (C(7)F(15)CH(2)CH(2)CO(2)H) are major products from 6:2 FTOH (C(6)F(13)CH(2)CH(2)OH) and 8:2 FTOH (C(8)F(17)CH(2)CH(2)OH) aerobic biotransformation, respectively. The 5:3 and 7:3 acids were dosed into domestic WWTP activated sludge for 90 d to determine their biodegradability. The 7:3 acid aerobic biodegradability was low, only 1.7 mol% conversion to perfluoroheptanoic acid (PFHpA), whereas no transformation was observed previously in soil. In stark contrast, 5:3 acid aerobic biodegradability was enhanced 10 times in activated sludge compared to soil. The 5:3 acid was not activated by acyl CoEnzyme A (CoA) synthetase, a key step required for further α- or ß-oxidation. Instead, 5:3 acid was directly converted to 4:3 acid (C(4)F(9)CH(2)CH(2)CO(2)H, 14.2 mol%) and 3:3 acid (C(3)F(7)CH(2)CH(2)CO(2)H, 0.9 mol%) via "one-carbon removal pathways". The 5:3 acid biotransformation also yielded perfluoropentanoic acid (PFPeA, 5.9 mol%) and perfluorobutanoic acid (PFBA, 0.8 mol%). This is the first report to identify key biotransformation intermediates which demonstrate novel one-carbon removal pathways with sequential removal of CF(2) groups. Identified biotransformation intermediates (10.2 mol% in sum) were 5:3 Uacid, α-OH 5:3 acid, 5:2 acid, and 5:2 Uacid. The 5:2 Uacid and 5:2 acid are novel intermediates identified for the first time which confirm the proposed pathways. In the biodegradation pathways, the genesis of the one carbon removal is CO(2) elimination from α-OH 5:3 acid. These results suggest that there are enzymatic mechanisms available in the environment that can lead to 6:2 FTOH and 5:3 acid mineralization. The dehydrogenation from 5:3 acid to 5:3 Uacid was the rate-limiting enzymatic step for 5:3 acid conversion to 4:3 acid.
authors.affiliation: E.I. du Pont De Nemours & Company, Inc., Wilmington, DE, USA. ning.wang@usa.dupont.com
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
authors.forename: Robert C
authors.initials: RC
authors.lastname: Buck
authors.forename: Bogdan
authors.initials: B
authors.lastname: Szostek
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Sulecki
authors.forename: Barry W
authors.initials: BW
authors.lastname: Wolstenholme
mesh_terms: D000332:Aerobiosis; D001711:Biotransformation; D002244:Carbon / Q000032:analysis / Q000378:metabolism; D005466:Fluorocarbons / Q000032:analysis / Q000378:metabolism*; D010088:Oxidoreductases / Q000032:analysis / Q000378:metabolism*; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism*
chemical_list: D005466:Fluorocarbons; D012722:Sewage; D014874:Water Pollutants, Chemical; D002244:Carbon; D010088:Oxidoreductases; C019825:carboxylic acid reductase