ERASE-PFAS: Microbial electrochemical defluorination of PFAS using bioaugmented Acidmicrobium sp. Strain A6

Per and polyfluorinated alkyl substances (PFAS) are emerging contaminants of concern because they are ubiquitous and have been linked to multiple health problems, including cancer. PFAS are extremely stable, and those of most concern have been considered non-biodegradable. This stability has led to these compounds being dubbed “forever chemicals.” Recently, the bacterium Acidimicrobium (A6) commonly found in acidic iron rich soils has been shown to degrade PFAS.

A6 uses ammonia for energy by reaction with solid-phase iron oxides. Although iron oxides are common in soils, adding them to bioreactors for the controlled growth of A6 is challenging. To address these challenges, a special bioelectrochemical reactor was developed with iron serving as the anode.

The goal of this project is to gain a fundamental understanding of how A6 degrades PFAS. This will be achieved through testing A6 with various PFAS and operational conditions using the specially formulated bioelectrochemical reactors to understand the mechanisms of PFAS biodegradation. Successful completion of this research will allow the rapid growth of A6 for subsequent addition (“bioaugmentation”) of A6 into contaminated soils to treat PFAS on site, or through direct treatment of PFAS-contaminated water in the bioreactors.

This project will train graduate students, undergraduate students, and involve STEM high school students during summer internships in the novel field of PFAS treatment. Results will be disseminated in scientific journals and conferences to advance knowledge. Outreach efforts are focused on advancing acceptance of this novel treatment technology through collaboration with a company to implement a demonstration project for testing in real world applications.

Acidimicrobium sp. Strain A6 (A6) is a novel autotrophic Gram-positive bacterium that oxidizes ammonium while reducing iron. A6 is capable of defluorinating PFAS, including perfluorinated compounds such as PFOA and PFOS.

The genome of A6 contains dehalogenase genes, including a reductive dehalogenase homolog and a fluoroacetate dehalogenase homolog that are both expressed when PFAS are defluorinated. The high demand of A6 for ferric iron makes it challenging to grow this strain in traditional bioreactors for extended periods of time. Fortunately, A6 is electrogenic and can grow in the absence of iron in microbial electrolysis cells, where it is also able to defluorinate PFOA.

This novel research focuses first on understanding the mechanisms by which A6 grows in bioelectrochemical systems. PFAS defluorination will be examined using both pure and enrichment cultures while tracking gene expression and degradation intermediates. Bioreactor results will be combined with results from batch incubations, and a separate collaboration with enzymologists to gain new insights into the mechanisms of PFAS defluorination by A6.

The project will train a PhD student and result in close collaboration between students from multiple laboratories to increase cross disciplinary collaboration. Summer engineering and high school interns will be recruited to work in the laboratories to increase STEM training. A collaboration with an industrial partner will implement a pilot demonstration of A6 bioaugmentation to degrade PFAS in industrial waste to facilitate implementation of these findings in the remediation field.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.