Citation:

Yang, S., Y. Shi, M. Strynar, AND K. Chu. Desulfonation and defluorination of 6:2 fluorotelomer sulfonic acid (6:2 FTSA) by Rhodococcus jostii RHA1: Carbon and sulfur sources, enzymes, and pathways. JOURNAL OF HAZARDOUS MATERIALS. Elsevier Science Ltd, New York, NY, 423(Part A):127052, (2022). https://doi.org/10.1016/j.jhazmat.2021.127052

Impact/Purpose:

The compound 6:2 FTSA (6:2 Fluorotelomer Sulfonic Acid) is an important PFAS as is is used in a majority of contemporary products including AFFF formulations and chromium plating anti-mist solutions. It is a commonly found PFAS impacted by both of these industries. The microbial degradation and pathways to metabolites is important in defining the co-occuring PFAS that may be associated. This study shows that the used microorganisims are able to completely degrade the 6:2 FTSA rapidly leading to a series of PFAS terminal metabolites. All parties interested in PFAS contamination by this compound and remediation would have an interest in this topic.

Description:

6:2 fluorotelomer sulfonic acid (6:2 FTSA) is one per- and poly-fluoroalkyl substances commonly detected in the environment. While biotransformation of 6:2 FTSA has been reported, factors affecting desulfonation and defluorination of 6:2 FTSA remain poorly understood. This study elucidated the effects of carbon and sulfur sources on the gene expression of Rhodococcus jostii RHA1 which is responsible for the 6:2 FTSA biotransformation. While alkane monooxygenase and cytochrome P450 were highly expressed in ethanol-, 1-butanol-, and n-octane-grown RHA1 in sulfur-rich medium, these cultures only defluorinated 6:2 fluorotelomer alcohol but not 6:2 FTSA, suggesting that the sulfonate group in 6:2 FTSA hinders enzymatic defluorination. In sulfur-free growth media, alkanesulfonate monooxygenase was linked to desulfonation of 6:2 FTSA; while alkane monooxygenase, haloacid dehalogenase, and cytochrome P450 were linked to defluorination of 6:2 FTSA. The desulfonation and defluorination ability of these enzymes toward 6:2 FTSA were validated through heterologous gene expression and in vitro assays. Four degradation metabolites were confirmed and one was identified as a tentative metabolite. The results provide a new understanding of 6:2 FTSA biotransformation by RHA1. The genes encoding these desulfonating- and defluorinating-enzymes are potential markers to be used to assess 6:2 FTSA biotransformation in the environment.

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