Bacterial degradation of perfluorooctane sulfonic acid (PFOS): detection of by-products by target and non-target analysis

Introduction: Per- and poly-fluoroalkyl substances (PFAS) are highly fluorinated synthetic chemicals with a wide variety of uses1,2. The carbon- fluorine bonds exhibit very high bond dissociation energies: around 536 kJ/mol, making PFAS generally resistant to degradation by oxidation, thermal treatment, and biological mechanisms, which has led to their classification as “forever chemicals”3. Strategies to enhance the biodegradation of these compounds are of great interest, such as identifying bacterial species that may be used for bioaugmentation. Labrys portucalensis F11 is an aerobic bacterium that has been isolated in Portugal and can degrade fluorinated pharmaceuticals, fluorobenzene, and fluoxetine4,5. This F11 strain has the ability to cleave C-F bonds in these fluorinated organic compounds and was therefore tested for its ability to degrade perfluorooctane sulfonate (PFOS), the most frequently detected PFAS in the environment. Objectives: To determine whether the F11 bacteria strain can degrade PFOS; To identify biodegradation products by non-targeted analysis. Conclusions: Labrys portucalensis strain F11 degraded PFOS. Shorter-chain PFAS, from C7 to C3 were formed as metabolites. Non-target analysis facilitated the identification of the unsaturated and hydrogenated C8 compounds. IMS separation exhibited the separation of isomers of PFOS as well as defluorinated PFOS isomers including isomers of H-PFOS and isomers of unsaturated PFOS.