In situ destruction of halogenated Superfund contaminants with biological radical reactions

PROJECT 3: SUMMARY/ABSTRACT
Highly halogenated compounds include recently recognized pollutants such as per- and polyfluorinated alkyl
substances (PFAS) as well as legacy contaminants, such as chlorinated solvents, polychlorinated biphenyls
(PCBs) and Polybrominated diphenyl ethers (PBDEs). PFAS and other extremely persistent halogenated
compounds do not exist alone in sites. For example, chlorinated solvents (e.g., trichloroethylene) often coexist
with 1,4-dioxane and PFAS, as well as fuel components including benzene and xylene. Highly halogenated
compounds remain in sites even when co-contaminants have been remediated, posing continued environmental
health risks to human receptors through exposure via drinking water sources and food. As more highly
halogenated chemicals are discovered, remediation strategies need to combine both selectivity and high
reactivity. For decades bioremediation has been attractive due to selective enzymes targeting specific
contaminants. Likewise, chemical redox treatment has garnered interest due to its high reactivity. However, it
takes decades to evolve new specific enzymes in nature and the harsh site conditions after chemical treatment
are drawbacks to both technologies when applied alone. Biological enzymatic systems that produce radicals are
widespread in microbial systems in aerobic and anaerobic environments. We hypothesize that these biological-
radical systems could become a novel remediation approach that combines both selectivity and high
reactivity.
In Aim 1, we propose to employ bioinformatics and molecular biology techniques to study known and putative
laccase systems with multiple chemical mediator compounds in high throughput assays to determine optimized
systems for PFAS treatment. Aim 2 focuses on studying the reactions of anaerobic radical systems, such as
glycyl radical enzymes (GRE) and S-adenosylmethionine (SAM) to study their capability to be engineered future
remediation strategies. We will combine Project 3 and 4 approaches in Aim 3, where chemical treatment will be
used to prime pollutants that make them more amenable to subsequent biological radical treatment, as well as
study the microbial community dynamics before and after chemical treatment. The findings of Project 3 could
provide a new approach of remediation technologies to remediate highly halogenated emerging and legacy
compounds in the environment to protect the environmental health of surrounding communities.

Grant Number: 4P42ES004705-37
NIH Institute/Center: NIH
Principal Investigator: Lisa Alvarez-Cohen