A team of environmental engineering experts at the University of California Riverside has discovered specific bacteria that can destroy certain types of per- and polyfluoroalkyl substances (PFAS), representing an important step towards more affordable methods for purifying contaminated drinking water sources.

These bacteria, which belong to the genus Acetobacterium, are commonly found in wastewater environments worldwide.

PFAS, also known as "forever chemicals," are named for their extremely stable carbon-fluorine bonds, which allow them to persist in the environment for long periods.

According to research published in the journal Science Advances, scientists at the University of California Riverside and their collaborators have discovered that these bacteria can break the strong bonds between fluorine and carbon.

New Advances in Understanding PFAS
"We have discovered for the first time a bacterium that can carry out the reductive defluorination of PFAS structures," said Yujie Men, the lead author of the study and associate professor in the Department of Chemical and Environmental Engineering at the Bourns College of Engineering at UCR.

Men emphasized that these bacteria are effective only on unsaturated PFAS compounds, which have double bonds between carbon atoms in their chemical structure.

Scientists also identified specific enzymes in these bacteria that are key to breaking the bonds between carbon and fluorine. This discovery opens possibilities for bioengineers to enhance these enzymes to be more effective on other PFAS compounds. (Enzymes are proteins that act as catalysts for biochemical reactions.)

Potential for Bioengineering
"If we can understand the mechanism, we might be able to find similar enzymes based on the identified molecular properties and select more effective ones," Men said. "Also, if we can design a new enzyme or modify a known enzyme based on mechanistic understanding, we could make it more effective and capable of working with a wider range of PFAS molecules."

Last year, Men published a paper identifying other microorganisms that break the bonds between carbon and chlorine in chlorinated PFAS compounds, which triggers significant spontaneous defluorination and destroys this group of pollutants. The latest discovery significantly expands the number of PFAS compounds that can be biologically destroyed.

Economical Method for Water Purification
Using bacteria to treat groundwater is economically viable because microorganisms destroy pollutants before the water reaches wells. The process involves injecting groundwater with selected bacterial species along with nutrients to increase their numbers.

Given that PFAS compounds are linked to cancer and other health issues, the U.S. Environmental Protection Agency (EPA) imposed water quality limits this year, restricting certain forever chemicals to just four parts per trillion in tap water, prompting water providers to find solutions for cleaning PFAS.

PFAS compounds have been widely used in thousands of consumer products since the 1940s due to their ability to resist heat, water, and lipids. Examples of products containing PFAS include firefighting foams, grease-resistant paper wrappers and containers such as microwave popcorn bags, pizza boxes, and candy wrappers; also, stain and water repellents used on carpets, upholstered furniture, clothing, and other fabrics, according to the EPA.

The title of the paper is "Bifurcating Electron and Fluoride Efflux Systems in Acetobacterium Species Drive Defluorination of Perfluorinated Unsaturated Carboxylic Acids." Yaochun Yu is the lead author. He was a visiting student researcher and postdoctoral fellow at UCR before joining the Swiss Federal Institute of Aquatic Science and Technology (Eawag) in 2022.

In addition to Yu and Men, the co-authors are Fengjun Xu, Weiyang Zhao, Calvin Thoma, Shun Che, Jack E. Richman, Bosen Jin, Yiwen Zhu, Yue Xing, and Lawrence Wackett.

Source: UNIVERSITY OF CALIFORNIA