Leveraging Yeast to Filter Lead from Drinking Water

Even at extremely low concentrations—just a few parts per billion—lead can be toxic when it is present in drinking water. And when lead is discovered in the water supply, as seen in Flint, Mich., remediation can be not only costly, but time-consuming. Now, researchers at the Georgia Institute of Technology have found a surprising environmentally friendly biofilter that can remove lead from water: yeast.

“There were some studies in the 1980s that suggested that different microbes might be able to capture heavy metals,” said Christos Athanasiou, an assistant professor at the Daniel Guggenheim School of Aerospace Engineering. “Yeast also happens to be a microbe that you can find in abundance that is a byproduct in a lot of fermentation industries, like brewing and also biofuels and biomaterials.”

Yeast as biosorbent

Athanasiou, and Patricia Stathatou, an assistant professor at the School of Chemical and Biomolecular Engineering, while still working at the Massachusetts Institute of Technology (MIT), first worked to “decipher” the fundamental process that allow Saccharomyces cerevisiae, a type of yeast, to pick up lead in water. They found its cell wall acts as a biosorbent, which can achieve an uptake of up to 12 mg of lead per gram of biomass in solutions where the lead concentration is below 1 part per million. 

Yet, Stathatou said, it’s not enough to just throw yeast in the water supply. You need to be able to extract the absorbed lead and that requires some type of housing. “We needed to find a way to encapsulate the yeast in something so we could make a filter out of it,” she said. “We then worked to put it into a hydrogel so we could scale up the system and make it robust enough so that it could hold up to the mechanics of water flow.”

The pair, along with collaborators from MIT’s chemical engineering department, Devashish Gokhale and Patrick S. Doyle, came up with a design not unlike a multivitamin capsule. The hydrogel exterior is porous enough to allow the water, including the lead, to reach the yeast inside—but not so pervious to permit the yeast, even once they have captured the lead, to make an escape. 

Robust design

“With this approach, with a capsule that was void in the middle and kept the yeast in the void, the yeast could freely interact with the water as it came through without being bounded by the hydrogen all around,” Stathatou said. “It took us several months to come up with the right design and overcome the challenges—and then do the mechanical testing to make sure that it could hold up over time in an environment where there is running water.”

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Now that the research team has determined that this design is robust enough to operate continuously while withstanding the forces of water for up to 12 days, they say it could one day be used in one of several ways. Consumers could potentially put a small yeast-powered biofilter over their kitchen faucets—or the design could even be scaled up to create larger filters that freely float in municipal or industrial wastewater treatment plants. 

Next steps

But Athanasiou believes microbes can do more than just purify water. He believes there may be multiple space applications for yeast biofilters in the future. 

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“There may be applications for space mining and finding heavy metals or other minerals,” he said. “It’s a bundle—but microbes are very light, like a powder. Sending things to space is very expensive. So having to send a few grams of yeast would be easier than other types of mining equipment. We could try to use it as a way to mine resources or identify specific metallic compounds in space.” 

Stathatou added that such filters could also be used to one day filter other types of pollutants like per- and polyfluoroalkyl substances (PFAS). It is ongoing research, but she thinks it has great promise.

“This is an environmentally friendly solution from the cradle to the grave,” she said. “These yeasts are readily available and something that are just being thrown away. And they have the potential to not only reclaim pollutants but be reused several times before they lose their performance. They offer us a way to get rid of many pollutants at lower costs in a very sustainable way—and in a way that can be produced all over the globe.”

Kayt Sukel is a technology writer and author in Houston.