When PFAS (per- and polyfluoroalkyl substances) were developed, companies found a huge number of ways to apply them to different products. But while they have desirable properties, they have also had a massively negative impact on various parts of the environment. Because they are so tough, they have made their way into water supplies and soils, and it is very difficult to remove them. These so-called forever chemicals are now having a detrimental impact on human, animal, and environmental health.
Some research has identified bacterial species that can break the tough bonds in forever chemicals, however, and may offer a potential solution for removing these chemicals from various places, such as wastewater.
But much of this research has not considered the byproducts that are generated when bacteria break down forever chemicals. A new study has accounted for these byproducts, however, and has found bacteria that can not only break the bonds of forever chemicals, but can also deal with the downstream molecules that are created in those reactions. The findings have been reported in Science of the Total Environment.
This work determined that a bacterium called Labrys portucalensis F11 (F11) was able to metabolize more than 90 percent of a forever chemical called perfluorooctane sulfonic acid (PFOS), and it did so within 100 days. PFOS is one of the more common types of forever chemicals, and it is hazardous. The bacterium also degraded a large part of two other PFAS chemicals; about 58 percent of 5:3 fluorotelomer carboxylic acid were broken down while 21 percent of 6:2 fluorotelomer sulfonate was degraded. F11 could eliminate some of the shorter chain metabolites completely, and removed fluorine or took it down to undetectable levels too.
"The bond between carbon and fluorine atoms in PFAS is very strong, so most microbes cannot use it as an energy source. The F11 bacterial strain developed the ability to chop away the fluorine and eat the carbon," said corresponding study author, Diana Aga, PhD, the Chair of the Department of Chemistry at the University at Buffalo, among other appointments.
Bacteria don't generally want to eat PFAS, but those that can exist in an extremely polluted environment can adapt to it. "Through evolution, some bacteria can develop effective mechanisms to use chemical contaminants to help them grow," explained first study author, Mindula Wijayahena, a graduate student in the Aga lab.
The F11 strain was isolated from contaminated soil at a Portuguese industrial site. While previous work has shown that it can remove fluorine from toxic contaminants, this work investigated its effects on PFAS.
The researchers did so by adding F11 to flasks that contained 10,000 micrograms of PFAS per liter, and no other carbon source. The bacterium could break a very tough carbon-fluorine bond, which is a crucial step, noted Wijayahena. "Crucially, F11 was not only chopping PFOS into smaller pieces, but also removing the fluorine from those smaller pieces."
One caveat of this study is that while the microbes could break down PFAS, there were also no other carbon sources to tempt them, and they had nothing else to consume. So the researchers want to find ways to boost PFAS consumption in F11.
It may one day be possible to use F11 to decontaminate water or soil that is contaminated with PFAS.
"In wastewater-activated sludge systems, you could accelerate removal of undesired compounds by adding a specific strain to the existing bacterial consortium in the treatment plants," Aga said.
Sources: University of Buffalo, Science of the Total Environment
