PROJECT SUMMARY
Environmental contamination by per- and polyfluoroalkyl substances (PFASs) is a major public health concern
because of the wide range of toxic effects that have been associated with exposure to these persistent chemicals.
Due to the strong stability of the C-F bond, very few microorganisms have been found capable of degrading
PFASs, and the biodegradation is very slow and incomplete. Often, bioremediation efforts result in the formation
of shorter chain PFASs that remain toxic, persistent, and highly mobile in the environment. Current abiotic
treatment technologies can be more effective, but have very high energy requirements. Therefore, this research
proposes an innovative remediation strategy that couples a pre-treatment step using catalytic hybrid
nanomaterials with biodegradation using enriched microbial communities to achieve more efficient and complete
destruction of PFASs without the formation of toxic by-products. Multifunctional reduced graphene oxide-metallic
nanohybrids (e.g. rGO-nZVI-TiO2) that are capable of catalyzing defluorination and oxidation of PFASs will be
synthesized and characterized for their efficiencies in converting highly stable PFASs to more biodegradable
forms. Pure cultures (e.g. Dehalococcoides sp. and Dehalobacter sp.) and enriched microbial consortia collected
from PFAS-contaminated sites and anaerobic wastewater treatment plants will be used to degrade different
types of PFASs and measure their removal efficacy. Using metagenomic and transcriptomic tools, the
microorganisms responsible for degradation, their functional characteristics, and the genes being transcribed
during defluorination will be identified. By-products formed at each step of the pre-treatment reaction, and during
the course of the microbial degradation of PFASs will be characterized using liquid chromatography with high-
resolution mass spectrometry, 19F-nuclear magnetic resonance spectroscopy, and ion chromatography to obtain
information on the identities of PFASs transformation products, degradation kinetics, and mass balance.
Molecular modeling will be used to bring mechanistic insight into specific PFAS-surface and PFAS-enzyme
interactions. The effect of the structural features of PFASs (i.e. branching, chain-length, type of head groups) on
their biodegradability will be systematically evaluated, first by molecular modeling, and then by experimental
validation. Knowledge from the chemical characterization of PFASs degradation by-products combined with in
silico site-directed mutagenesis will facilitate the tuning of enzymatic activities and discovery of novel bacteria
that are efficient degraders of PFASs from the natural environment. These insights will guide the systematic
design of highly efficient nano-enhanced bioremediation systems for complete microbial degradation of PFASs.
