Isolation, identification, and degradation characteristics of perfluorooctane sulfonamide-degrading bacterium

Abstract:

[Background] Per-and poly-fluoroalkyl substances (PFAS), a class of organic pollutants with high surface activity, thermal stability, chemical stability, hydrophobicity, and lipophobicity, are difficult to be degraded. Due to the long-distance migration, strong environmental persistence, and bioaccumulation, PFAS has brought serious harm to the environment and organisms. [Objective] To isolate an efficient perfluorooctane sulfonamide (PFOSA)-degrading bacterium from a sewage treatment plant and analyze the degradation characteristics and mechanism. [Methods] An aerobic PFOSA-degrading bacterium was screened out from wastewater by enrichment, isolation, and purification with PFOSA as the sole carbon source. The strain was identified by morphological observation and 16S rRNA gene and whole-genome sequencing. The degradation rate and degradation products of PFOSA were analyzed by a triple quadrupole mass spectrometer. [Results] An aerobic PFOSA-degrading bacterium C11 was isolated and identified as Comamonas testosteroni. The single factor experiments for degradation condition optimization showed that the degradation rate of PFOSA by strain C11 reached 64.6% under the optimal conditions of 30 ℃, pH 7.0, and PFOSA concentration of 30 mg/L. The degradation products of PFOSA were perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorodecanoic acid (PFHpA), and perfluorohexanoic acid (PFHxA). According to the degradation products, we preliminarily hypothesized the degradation pathway of strain C11. Specifically, PFOS generated from the deamination of PFOSA was desulfonated and oxidized to PFOA, which was then converted into PFHpA and PFHxA after the cleavage of C–F bond. [Conclusion] Strain C11 has a strong ability of degrading PFOSA, which provides theoretical support for deciphering the biodegradation mechanism of PFOSA and exploring the bioremediation path of PFAS-contaminated environment.