001

Title:

Biotransformation and Biodefluorination of FTCAs by Actinomycetes

Discipline: Environmental Science

Presenter:

Chen Wu

Abstract:

Fluorotelomer carboxylic acids (FTCAs, e.g., 6:2 FTCA and 5:3 FTCA) have been widely detected in the environment, especially in landfill leachates since they are common ingredient compounds of surfactant industry and essential metabolic intermediates for the biotransformation of various PFASs precursors. Aerobic degradation of FTCAs generates an array of perfluorinated carboxylic acids (PFCAs, e.g., PFHxA and PFBA) that are highly persistent and bioaccumulative once enter the food chain. In this study, we investigated the biotransformation and biodefluorination of 6:2 FTCA and 5:3 FTCA in 7 selected Actinomycetes, including Mycobacterium dioxanotrophicus PH-06, Mycobacterium smegmatis mc2-155, Rhodococcus jostii RHA1, and 4 more Rhodococcus strains. RHA1 exhibited the best 6:2 FTCA biotransformation activity than the other 6 species. However, monitoring of free fluoride and biotransformation metabolites revealed distinct biodefluorination potentials and pathways between 6:2 FTCA and 5:3 FTCA. After 48 hours of exposure, complete 6:2 FTCA removal was observed by RHA1. In the interim, free fluoride in the media mounted up to a concentration of 0.116 mM. We further analyzed the biotransformation metabolites using High-Resolution Mass Spectrometry (HRMS) equipped with the nano-electrospray ionization (Nano-ESI) injection. More than 10 PFASs were detected as the metabolites of 6:2 FTCA biotransformation, such as PFHpA, 6:2 FTUCA, 5:3 FTCA, 5:3 Uacid, α-OH 5:3FTCA, PFHxA, and PFPeA. Detection of these less fluorinated metabolites supports the observed defluorination. However, mass balance based on total fluoride revealed the existence of unknown intermediates accounting for the dominant products resulted from 6:2 FTCA biotransformation. In contrast, minimal fluoride release (less than 0.001 mM) was detected during 5:3 FTCA biotransformation by RHA1, though over 90% of 5:3 FTCA removal was identified. Accordingly, no conventional defluorination metabolites of 5:3 FTCA were significantly detected in comparison with the blank controls, suggesting some non-defluorinated metabolites were formed during 5:3 FTCA biotransformation. We are in the process of untangling these unknown metabolites of FTCA biodefluorination using non-target HRMS workflow. Our research is of fundamental scientific value to advance our understanding of biodefluorination mechanisms and promote the development of cost-efficient biological treatment strategies to remove FTCA contamination with optimized defluorination and minimized accumulation of PFCAs and other persistent compounds.

Author(s):

Chen Wu, Qi Wang, Hao Chen, Mengyan Li

Funding Acknowledgements:

USGS, NJWRRI