Dominant Pathways and Key Intermediates in the Biotransformation of Perfluoroalkane Sulfonamide Derivatives Revealed by Integrated Kinetics Analyses

There is interest in assessing the occurrence and biotransformation potential of per- and polyfluoroalkyl substances (PFASs) in the environment. Perfluoroalkane sulfonamide derivatives are a class of PFASs that have received attention due to their widespread use and environmental persistence. The goals of this research were to integrate studies of PFAS biotransformation pathways and biotransformation kinetics to discover dominant biotransformation pathways, enable quantitative estimates on the formation of rate-limiting intermediates, and simulate the net formation of key biotransformation products. We selected eight perfluoroalkane sulfonamide derivatives and performed aerobic batch experiments in bioreactors seeded with wastewater microbial communities. We identified 71 biotransformation products among the parent compounds, of which 42 represent unique chemical structures. We found that the biotransformation products could be assembled into convergent biotransformation pathways that generalize our understanding of the way perfluoroalkane sulfonamide derivatives are biotransformed. Our kinetics analyses reveal the dominant branches in the biotransformation pathways and allowed us to quantitatively estimate the extent of formation and biotransformation rate constant of key rate-limiting intermediates in the absence of authentic standards. Our results contribute to the ongoing discovery of biotransformation products for classes of PFASs and provide essential kinetics data to simulate the net formation of key biotransformation products.