Cometabolic defluorination of two poly-fluoroalkyl substances by a new Sphingopyxis isolate

Microbial defluorination of per- and poly-fluoroalkyl substances (PFAS) likely involves cometabolic degradation. The isolation of pure cultures capable of this cometabolism would enhance our understanding of microbial defluorination mechanisms. Here, a novel isolate Sphingopyxis sp. strain NJF-3 was isolated and used to investigate the cometabolic defluorination of two poly-fluoroalkyl substances, 4,5,5-trifluoropent-4-enoic acid (TFEA) and 4,4,4-trifluoro-3-(trifluoromethyl)crotonic acid (SFCA). The isolate utilized 1-fluorodecane (FD) as the sole carbon source and released 873 ± 55 μM of inorganic fluoride (F⁻) from 1 mM FD within a 7-day incubation. The cometabolism of TFEA and SFCA by strain NJF-3 were significantly dependent on bacterial growth. Eleven cometabolic substrates were tested, revealing that 3,3-dimethylacrylic acid significantly stimulated TFEA defluorination, resulting in the removal of 27.3 ± 1.8 μM TFEA and the release of 71 ± 2.7 μM F⁻ over 28 days of incubation. Ammonium acetate promoted SFCA defluorination, leading to the degradation of 183 ± 17 μM SFCA and the release 736 ± 8.3 μM of F⁻ following 60 days of incubation. The integration of intermediate analysis with genomic data of strain NJF-3 revealed that the cometabolic biodefluorination proceeds via β-oxidation pathway, with hydroxylation-dehydration steps likely crucial for enzymatic C-F bond cleavage.