Superfund Research Program
Model-aided Design and Integration of Functionalized Hybrid Nanomaterials for Enhanced Bioremediation of Per-and Polyfluoroalkyl Substances (PFASs)
Environmental contamination by per- and polyfluoroalkyl substances (PFAS) 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 carbon-fluorine 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.
This project 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 PFAS without the formation of toxic by-products. Multifunctional reduced graphene oxide-metallic nanohybrids that are capable of catalyzing defluorination and oxidation of PFAS will be synthesized and characterized for their efficiencies in converting highly stable PFAS to more biodegradable forms. Pure bacteria cultures and enriched microbial consortia collected from PFAS-contaminated sites and anaerobic wastewater treatment plants will be used to degrade different types of PFAS 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 PFAS 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 PFAS 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 PFAS, such as branching, chain-length, and 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. Insight from this project will guide the systematic design of highly efficient nano-enhanced bioremediation systems for complete microbial degradation of PFAS.