Strategies for the Biodegradation of Polyfluorinated Compounds

Abstract

Many cite the strength of C–F bonds for the poor microbial biodegradability of polyfluorinated organic compounds (PFCs). However, commercial PFCs almost invariably contain more functionality than fluorine. The additional functionality provides a weak entry point for reactions that activate C–F bonds and lead to their eventual cleavage. This metabolic activation strategy is common in microbial biodegradation pathways and is observed with aromatic hydrocarbons, chlorinated compounds, phosphonates and many other compounds. Initial metabolic activation precedes critical bond breakage and assimilation of nutrients. A similar strategy with commercial PFCs proceeds via initial attack at the non-fluorinated functionalities: sulfonates, carboxylates, chlorines, phenyl rings, or phosphonates. Metabolic transformation of these non-fluorinated groups can activate the C–F bonds, allowing more facile cleavage than a direct attack on the C–F bonds. Given that virtually all compounds denoted as “PFAS” are not perfluorinated and are not alkanes, it is posited here that considering their individual chemical classes is more useful for both chemical and microbiological considerations of their fate.

A Review: Per- and Polyfluoroalkyl Substances—Biological Degradation

“…The additional functionality (chlorines, phenyl rings, sulfonates, carboxylates, or phosphonates) provides a weak entry point for reactions that activate C–F bonds and lead to their eventual cleavage. When additional functionality is attached to a highly fluorinated, even perfluorinated, chain or ring, there are other chemical and metabolic possibilities available to achieve defluorination [ 92 ].…”

About Perfluoropolyhedranes, Their Electron‐Accepting Ability and Questionable Supramolecular Hosting Capacity

“…The practicality of this approach in terms of remediation may, however, not be obvious [172] . Strategies for the biological degradation of functionalized polyfluorinated materials have been reviewed, [173] and considerable efforts are deployed for environmental remediation [174] . Anyhow, the development of highly fluorinated materials is only conceivable for small tonnage products for which benefits and performances are critical and cannot be attained otherwise.…”

Silver(i) Perfluoroalcoholates: Synthesis, Structure, and their Use as Transfer Reagents

“…Particularly, trifluoromethoxylation is a useful tool to tune the lipophilicity and metabolic stability, and to influence the conformation of bioactive compounds [2] . Unlike other fluorinated groups, the −OCF 3 group has the advantage of being degradable into non‐persistent compounds, like CO 2 and HF [8–10] . Due to the high stability, mobility, and toxicity of some PFAS (per‐ and polyfluorinated alkyl substances), the EU demands a ban of these PFAS with some exceptions, especially for substances with −OCF 3 groups and for agrochemicals and pharmaceuticals [11] .…”