Evolutionary obstacles and not C–F bond strength make PFAS persistent

Abstract

The fate of organic matter in the environment, including anthropogenic chemicals, is largely predicated on the enzymatic capabilities of microorganisms. Microbes readily degrade, and thus recycle, most of the ~100,000 commercial chemicals used in modern society. Per‐ and polyfluorinated compounds (PFAS) are different. Many research papers posit that the general resistance of PFAS to microbial degradation is based in chemistry and that argument relates to the strength of the C–F bond. Here, I advance the opinion that the low biodegradability of PFAS is best formulated as a biological optimization problem, hence evolution. The framing of the problem is important. If it is framed around C–F bond strength, the major effort should focus on finding and engineering new C–F cleaving enzymes. The alternative, and preferred approach suggested here, is to focus on the directed evolution of biological systems containing known C–F cleaving systems. There are now reports of bacteria degrading and/or growing on multiply fluorinated arenes, alkenoic and alkanoic acids. The impediment to more efficient and widespread biodegradation in these systems is biological, not chemical. The rationale for this argument is made in the five sections below that follow the Introduction.

Burning question: Rethinking organohalide degradation strategy for bioremediation applications

“…To date, only limited aerobic and anaerobic strains or microcosms have been identified to be capable of degrading PFASs, and their transformation mechanisms remain unclear (Jin et al., 2023 ; Yu et al., 2022 ). However, as the fastest‐evolving cellular form of life, prokaryotes may naturally evolve their catabolic capability to degrade polyfluorinated compounds (Wackett, 2021 , 2024 ). One potential solution is to enrich and isolate new OHRB from extreme environments (Wackett, 2023 ).…”

“…These challenges necessitate an expansion of the diversity of microorganisms capable of metabolizing these pollutants (Xu et al., 2023 ). For instance, there is limited information available on the biodegradation of per‐ and polyfluoroalkyl substances (PFASs), and ongoing efforts are required to identify microbes being capable of efficiently degrading and detoxifying these polyfluorinated pollutants (Jin et al., 2023 ; Wackett, 2022 ; Wackett, 2024 ; Yu et al., 2022 ). In contrast, recent advancements in methodology and technology have facilitated the isolation and cultivation of new microorganisms, providing new avenues for the discovery of functional microorganisms for bioremediation of organohalide pollution (Lewis et al., 2021 ; Liang et al., 2022 ).…”