[Isolation, Identification, and Biodegradation Behaviors of a Perfluorooctane Sulfonic Acid Precursor (PreFOSs) Degrading Bacterium from Contaminated Soil]

Transformation of perfluorooctane sulfonate (PFOS) precursors (PreFOSs) is considered an additional source of PFOS in the environment and biota. A PreFOSs-degrading bacterium PF1, which was able to utilize PreFOSs as the sole carbon and energy source for growth, was isolated from contaminated soil collected from the surroundings of a fluoride factory. According to its morphology and 16S rDNA gene sequence analysis, strain PF1 was identified as Hyphomicrobium sp. The degradation rates of perfluorooctane sulfonamide (PFOSA) and N-ethyl perfluorooctane sulfonamide (N-EtFOSA) by PF1 were 14.6% and 8.2% (30℃; pH=7.0-7.2), respectively, whereas PF1 was unable to degrade PFOS. PFOSA could be biodegraded to PFOS. N-EtFOSA could be biodegraded to perfluorooctane sulfonamide acetic acid (FOSAA), PFOSA, and PFOS; PFOS was the predominant metabolite. Based on the above analysis, the proposed metabolic pathway of PFOSA by strain PF1 is deamination to form PFOS. Two possible degradation pathways are proposed for N-EtFOSA: ① deethylation of N-EtFOSA to produce PFOSA, followed by deamination to form PFOS, and ②oxidation of N-EtFOSA to FOSAA followed by sequential dealkylation to produce PFOSA, and then transformation to PFOS by deamination.