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. However, the finding was derived exclusively from studies on microbial communities that may complicate our understanding of microbiological mechanisms. Here, a novel isolate Sphingopyxis sp. strain NJF-3 was isolated and used to investigate cometabolic defluorination of two poly-fluoroalkyl substances, 4,5,5-trifluoropent-4-enoic acid (TFE) and 4,4,4-trifluoro-3-(trifluoromethyl) crotonic acid (SFC). The isolate utilized 1 fluorodecane (FD) as the sole carbon source and released 87.3 ± 5.4% of inorganic fluoride (F?) within a 7-day incubation. Cometabolism of TFE and SFC by strain NJF-3 were significantly dependent on bacterial growth. Among tested primary substrates, 3,3-dimethylacrylic acid significantly stimulated TFE defluorination, resulting in 27.3 ± 1.8% removal and 23.7 ± 0.9% of F? release over 28 days of incubation. In contrast, ammonium acetate enhanced transformation of 36.6 ± 3.3% of SFC, releasing 24.5 ± 0.3% of F? within 60 days. Integration of intermediate analysis with genomic data of strain NJF-3 revealed that the cometabolic biodefluorination proceeds via both a- and ß-oxidation pathways, with hydroxylation-dehydration steps likely crucial for enzymatic C–F bond cleavage.