Wijayahena, the study's first author, analyzed the samples containing PFAS and the bacteria following incubation in Portugal. Photo: Meredith Forrest Kulwicki/University at Buffalo
Researchers at the University of Buffalo are leveraging bacteria to take the “forever” out of “forever chemicals.” In a new study, they identified a strain of bacteria that can break down and transform at least three types of PFAS, including the toxic PFOS.
In PFAS, the bond between carbon and fluorine atoms is so strong that most microbes cannot use the carbon as an energy source.
However, scientists found that Labrys portucalensis F11 (F11) is different—at least under specific conditions.
In an experimental study published in Science of the Total Environment, researchers isolated F11 from soil gathered from a contaminated site in Portugal. They placed the bacteria in sealed flasks with no carbon source beside the 10,000 mg per liter of PFAS.
Following an incubation period of between 100 to 194 days, the samples revealed that F11 metabolized over 90% of PFOS. The bacteria also broke down a substantial portion of two additional types of PFAS: 58% of 5:3 fluorotelomer carboxylic acid and 21% of 6:2 fluorotelomer sulfonate.
Additionally, the elevated levels of fluoride ions detected in the soils indicated that F11 had detached the PFAS’ fluorine atoms so that the bacteria could metabolize the carbon atoms.
“The carbon-fluorine bond is what makes PFAS so difficult to break down, so to break them apart is a critical step. Crucially, F11 was not only chopping PFOS into smaller pieces, but also removing the fluorine from those smaller pieces,” said Mindula Wijayahena, the study’s first author.
Some of the metabolites left behind still contained fluorine, but after being exposed to PFOS for 194 days, F11 had even removed fluorine from three PFOS metabolites.
PFAS is hardly the meal of choice for bacterium; however, some bacteria that live in contaminated soil have mutated to break down organic contaminants so they can use their carbon as an energy source. F11 was isolated from the soil of a contaminated industrial site in Portugal, and had previously demonstrated the ability to strip fluorine from pharmaceutical contaminants.
One limitation to the University of Buffalo study is that there was no other carbon source available in the sealed flask for F11 to consume—PFAS was the only option, and it took 100 days. The team says they now plan to research ways to encourage F11 to consume PFAS faster, even when there are competing energy choices.
“We want to investigate the impact of placing alternative carbon sources alongside the PFAS. However, if that carbon source is too abundant and easy to degrade, the bacteria may not need to touch the PFAS at all,” said the study’s corresponding author, Diana Aga, SUNY Distinguished Professor and director of the UB RENEW Institute. “We need to give the F11 colonies enough food to grow, but not enough food that they lose the incentive to convert PFAS into a usable energy source.”
Eventually, F11 could be deployed in PFAS-contaminated water and soil by creating conditions to grow the strain within activated sludge at a wastewater treatment plant, or even injecting the bacteria directly into the soil or groundwater of a contaminated site.