Microbes found to destroy certain ‘eternal chemicals’ by cleaving stubborn fluorine-to-carbon bonds

A UC Riverside environmental engineering team has discovered specific bacterial species that can destroy certain types of “forever chemicals,” a step further toward low-cost treatment of contaminated drinking water sources.

Microorganisms belong to the genus Acetobacterium and are commonly found in wastewater environments around the world.

Forever chemicals, also known as per- and polyfluoroalkyl substances, or PFAS, are so named because they have stubbornly strong carbon-fluorine chemical bonds that make them persistent in the environment.

Microorganisms discovered by UCR scientists and their collaborators can cleave those stubborn fluorine-to-carbon bonds, they report July 17 in the journal Scientific advances.

“This is the first discovery of a bacterium that can perform reductive defluorination of PFAS structures,” said Yujie Men, corresponding author of the study and associate professor in UCR’s Bourns College of Engineering in the Department of Chemical and Environmental Engineering.

The men warned that the bacteria were only effective on unsaturated PFAS compounds, which have carbon-carbon double bonds in their chemical structures.

But importantly, the researchers also identified specific enzymes in these bacteria necessary for cleaving carbon-fluorine bonds. This discovery opens the door for bioengineers to improve these enzymes so they can be effective on other PFAS compounds. (Enzymes are proteins that act as catalysts for biochemical reactions.)

“If we can understand the mechanism, we may be able to find similar enzymes based on the identified molecular features and uncover more efficient ones,” Men said. “Also, if we can design some new enzyme or change this known enzyme based on mechanistic understanding, we might be able to make it more efficient and work with a wider range of PFAS molecules.”

In 2023, Men published a paper that identified additional microorganisms that cleave the carbon-chlorine bond in chlorinated PFAS compounds, triggering substantial spontaneous defluorination and destroying this group of pollutants. The latest discovery greatly expands the number of PFAS compounds that can be biodegraded.

Using bacteria to treat groundwater is cost-effective because the microorganisms destroy pollutants before the water reaches the wells. The process involves injecting the groundwater with preferred species of bacteria along with nutrients to increase their numbers.

Because PFAS compounds have been linked to cancer and other human health ailments, the U.S. Environmental Protection Agency (EPA) introduced water quality limits earlier this year that limit certain forever chemicals to just four parts per trillion in water from of the country’s water supply, prompting water suppliers. find solutions to clean up PFAS.

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

Yaochun Yu is the lead author of the article. He was a visiting student scientist and UCR postdoctoral researcher at UCR before joining the Swiss Federal Institute of Water Science and Technology, or Eawag, in 2022.