UC Riverside environmental engineering team has discovered specific bacterial species that can destroy certain kinds of “forever chemicals,” advancing efforts toward low-cost treatments of contaminated drinking water sources.
The microorganisms belong to the genus Acetobacterium and are commonly found in wastewater environments worldwide. Forever chemicals, also known as per- and polyfluoroalkyl substances or PFAS, are so named because they have strong carbon-fluorine chemical bonds, making them persistent in the environment.
The microorganisms identified by UCR scientists and collaborators can cleave these fluorine-to-carbon bonds, they reported in the journal Science Advances.
“This is the first discovery of a bacterium that can do reductive defluorination of PFAS structures,” said Yujie Men, corresponding author of the study and associate professor at UCR’s Bourns College of Engineering in the Department of Chemical and Environmental Engineering.
Men noted the bacteria were effective only on unsaturated PFAS compounds, which have double carbon-to-carbon bonds in their chemical structures.
The scientists also identified the specific enzymes essential for cleaving the carbon-fluorine bonds, opening possibilities for bioengineers to enhance these enzymes for broader PFAS compound effectiveness. Enzymes are proteins that act as catalysts for biochemical reactions.
“If we can understand the mechanism, we might find similar enzymes based on identified molecular traits and screen out more effective ones,” Men said. “Also, with this mechanistic understanding, we may be able to design new enzymes or modify known ones to make them more efficient across a broader range of PFAS molecules.”
Last year, Men published a paper identifying other microorganisms that cleave the carbon-chlorine bond in chlorinated PFAS compounds, which triggers substantial spontaneous defluorination and destroys this group of pollutants. The most recent discovery expands the PFAS compounds that can be biologically destroyed.
Using bacteria to treat groundwater is cost-effective because microorganisms destroy pollutants before the water reaches wells. The process involves injecting groundwater with preferred bacteria species along with nutrients to increase their numbers.
Because PFAS compounds are linked to cancer and other human health issues, the U.S. Environmental Protection Agency, or EPA, set water-quality limits earlier this year, restricting certain forever chemicals to only four parts per trillion in tap water. This action has prompted water providers to seek PFAS cleanup solutions.
PFAS compounds became widely used in thousands of consumer products starting in the 1940s for their heat, water and lipid resistance. Examples include fire suppressant foams, grease-resistant paper wrappers and stain and water repellents for carpets, upholstery, clothing and other fabrics, according to the EPA.
The paper's title is “Electron-bifurcation and fluoride efflux systems in Acetobacterium spp. Drive defluorination of perfluorinated unsaturated carboxylic acids.”
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