A research team in the United States has discovered a type of bacteria that is capable of decomposing and transforming at least three types of persistent chemical substances known as Per- and polyfluoroalkyl substances (PFAS). What’s more important is that it can decompose and convert some toxic byproducts generated during the breaking of bonds, offering a potential solution to the pollution problems caused by PFAS.
PFAS were widely used in the 1950s in non-stick cookware coatings, waterproofing, oil-resistant coatings, food packaging, firefighting foam, cosmetics, and other products. Studies have found that they are difficult to degrade by the environment or bacteria due to their strong carbon-fluorine bonds, which can resist degradation methods such as incineration, ultrasonication, plasma oxidation, and electrochemistry, hence being called “forever chemicals.”
Scientists are hoping to use microorganisms to address the pollution issues caused by PFAS in water sources and soil, aiming to reduce the harm they cause to human health. However, the understanding of microorganisms degrading fluorinated compounds (especially PFAS) is limited, requiring more experiments to verify which microorganisms can carry out the degradation task.
A research team from the University at Buffalo in the United States and the Catholic University of Portugal discovered a bacterium named “Labrys portucalensis F11” that can degrade three types of PFAS pollutants. It can also use the degraded substances as a source of food for further breakdown. The research findings were published in the journal “Whole Environmental Science” in January.
The F11 bacteria they used originated from soil in Portugal heavily contaminated by industrial pollution. Scientists found that F11 has the ability to remove fluorine from pharmaceutical pollutants, but has not been tested for removal on PFAS before.
In this experiment, the researchers separately placed perfluorooctanesulfonic acid (PFOS), 6:2 FluoroTelomer sulfonic acid (6:2 FTS), and 5:3 FluoroTelomer carboxylic acid (5:3 FTCA) from the PFAS family into flasks, sealed them with F11 bacteria, and let them sit for nearly 200 days to observe how the bacteria decomposed these chemical substances.
The results showed that after 194 days, the removal rate of PFOS reached up to 96%, while 5:3 FTCA and 6:2 FTS were removed by 58% and 21% respectively after 100 days. Although some PFAS residues were still present in the flasks, this indicates that F11 can break apart the fluorine atoms from PFAS and metabolize the carbon atoms.
Furthermore, they found that PFOS was decomposed by the bacteria into substances such as perfluorohexanesulfonic acid (PFHpS), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), perfluorobutanoic acid (PFBA), and perfluoropropanoic acid (PFPrA).
PFOS was chosen as the target of the experiment mainly because it is often detected in the environment and biological samples, and it has a high bioaccumulative toxicity, currently designated as a hazardous substance by the Environmental Protection Agency (EPA) in the United States.
Researchers at the University at Buffalo stated that this research is a good starting point, and the team is further planning to study how to make the F11 bacteria consume PFAS more efficiently. They ultimately hope to formally introduce it into PFAS-contaminated soil and water sources to solve the pollution problems.
The corresponding author of the study, Diana Aga, a distinguished professor at the State University of New York and Chair of the Department of Chemistry at the University at Buffalo, in addition to serving as the Director of the Institute for Sustainable Environment, Energy, and Water Resources (RENEW), mentioned that, “The carbon-fluorine bond in PFAS is very strong, most microorganisms are unable to degrade them, while F11 demonstrates the ability to break the strong carbon-fluorine bonds and consume carbon.”
“I think some bacteria undergo mutations in chemical pollution environments, giving them special mechanisms to turn chemical pollutants into usable nutrients,” Dr. Aga elaborated.
Mindula Wijayahena, a PhD student from Dr. Aga’s lab and the first author of the study, stated, “Previous studies only focused on the degradation of PFAS, without considering the byproducts produced after PFAS decomposition. This time, we studied the byproducts of PFAS decomposition, and found that these substances can also be further degraded by bacteria. Most importantly, F11 not only cuts PFOS into pieces but also removes fluorine ions from these fragments.”
Dr. Aga explained, “It is important to note that there may be other metabolites present in these samples, these metabolites are very small to the extent that current detection methods cannot identify them.” “Special strains of bacteria can be added to wastewater activated sludge systems to accelerate the removal of harmful compounds because bioaugmentation is currently a promising method.”
This work was supported by the National Institute of Environmental Health Sciences, a branch of the National Institutes of Health in the United States. Other collaborators included the Catholic University of Portugal, the University of Pittsburgh, and Waters Corporation.