These microorganisms, identified as part of the genus Acetobacterium, are typically found in wastewater environments worldwide.
Forever chemicals, technically known as per- and polyfluoroalkyl substances (PFAS), are notorious for their robust carbon-fluorine bonds, making them persist in the environment.
Researchers from UCR and their collaborators have discovered that these bacteria can cleave those tough fluorine-to-carbon bonds, as detailed in the journal Science Advances on Wednesday, July 17.
"This is the first discovery of a bacterium that can do reductive defluorination of PFAS structures," said Yujie Men, the study's corresponding author and an associate professor at UCR's Bourns College of Engineering, Department of Chemical and Environmental Engineering.
Men noted that the bacteria are only effective on unsaturated PFAS compounds, characterized by double carbon-to-carbon bonds in their chemical makeup.
Crucially, the scientists also pinpointed the specific enzymes in these bacteria essential for breaking the carbon-fluorine bonds. This finding offers bioengineers the opportunity to enhance these enzymes to target a broader range of PFAS compounds. (Enzymes are proteins that catalyze biochemical reactions.)
"If we can understand the mechanism, maybe we can find similar enzymes based on the identified molecular traits and screen out more effective ones," Men said. "Also, if we can design some new enzyme or alter this known enzyme based on the mechanistic understanding, we could be able to make it more efficient and work with a broader range of PFAS molecules."
Last year, Men published a study identifying other microorganisms capable of breaking the carbon-chlorine bond in chlorinated PFAS compounds, leading to significant spontaneous defluorination and destruction of these pollutants. This latest discovery significantly broadens the scope of PFAS compounds that can be biologically degraded.
Using bacteria to treat groundwater is cost-effective, as these microorganisms destroy pollutants before the water reaches wells. The method involves injecting the groundwater with the selected bacteria species and nutrients to boost their population.
Due to the association of PFAS compounds with cancer and other health issues, the U.S. Environmental Protection Agency (EPA) imposed water-quality limits earlier this year, restricting certain forever chemicals to only four parts per trillion in tap water, driving the need for effective PFAS remediation methods.
PFAS compounds have been widely used in consumer products since the 1940s for their resistance to heat, water, and lipids. Products containing PFAS include fire suppressant foams, grease-resistant paper products such as microwave popcorn bags, pizza boxes, and candy wrappers; and stain and water repellents used on carpets, upholstery, clothing, and other fabrics, as stated by the EPA.
The paper's title is "Electron-bifurcation and fluoride efflux systems in Acetobacterium spp. Drive defluorination of perfluorinated unsaturated carboxylic acids." Yaochun Yu is the lead author. He was a visiting student scientist and post-doctoral scientist at UCR before joining the Swiss Federal Institute of Aquatic Science and Technology (Eawag) in 2022.
Research Report:Electron-bifurcation and fluoride efflux systems in Acetobacterium spp. drive defluorination of perfluorinated unsaturated carboxylic acids
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