Every year, beer breweries discard thousands of tons of surplus yeast. Researchers from MIT and Georgia Tech have discovered an innovative method to repurpose this yeast to absorb lead from contaminated water.

Using a process known as biosorption, yeast can quickly absorb even trace amounts of lead and other heavy metals from water. The researchers have demonstrated that yeast can be encapsulated within hydrogel capsules to create an effective filter for removing lead. These capsules allow for easy removal of the yeast once the water is purified.

“We have the hydrogel surrounding the free yeast that exists in the center, which is porous enough to let water come in, interact with yeast as if they were freely moving in water, and then come out clean,” explains Patricia Stathatou, a former postdoc at the MIT Center for Bits and Atoms, now a research scientist and incoming assistant professor at Georgia Tech’s School of Chemical and Biomolecular Engineering. “The fact that the yeast themselves are bio-based, benign, and biodegradable is a significant advantage over traditional technologies.”

This process could be applied to filter drinking water in homes or scaled up for water treatment plants. MIT graduate student Devashish Gokhale and Stathatou are the lead authors of the study, published in RSC Sustainability. Patrick Doyle, the Robert T. Haslam Professor of Chemical Engineering at MIT, is the senior author, with Christos Athanasiou, an assistant professor of aerospace engineering at Georgia Tech, also contributing.

The study builds on work initiated by Stathatou and Athanasiou in 2021, when Athanasiou was a visiting scholar at MIT’s Center for Bits and Atoms. They discovered that waste yeast from a single brewery in Boston could treat the city’s entire water supply. However, a challenge remained in removing the yeast after it absorbed the lead.

In a fortunate coincidence, the researchers presented their findings at the AIChE Annual Meeting in Boston in 2021, where Gokhale was showcasing his research on using hydrogels to capture micropollutants in water. The teams decided to collaborate, encapsulating yeast in hydrogels developed by Gokhale and Doyle.

“We decided to make these hollow capsules, similar to a multivitamin pill, but instead of filling them with vitamins, we fill them with yeast cells,” Gokhale explains. “These capsules are porous, allowing water to enter and interact with the yeast, which binds the lead, while the yeast remain contained.”

The capsules, made from polyethylene glycol (PEG), are about half a millimeter in diameter. They allow water to pass through and interact with the yeast inside, while keeping the yeast contained.

Led by Athanasiou, the researchers tested the mechanical stability of the capsules and found they could withstand forces similar to those generated by water running from a faucet and in water treatment plants. They constructed a proof-of-concept biofilter capable of treating lead-contaminated water continuously for 12 days, meeting U.S. Environmental Protection Agency drinking water guidelines.

This biosorption process consumes less energy than traditional methods such as precipitation and membrane filtration. Rooted in circular economy principles, this approach minimizes waste and environmental impact, offering economic opportunities to local communities. It holds significant potential for low-income areas historically affected by environmental pollution and limited access to clean water.

“We see an interesting environmental justice aspect to this, especially when starting with something as low-cost and sustainable as yeast,” Gokhale says.

The researchers are exploring strategies for recycling and replacing the yeast, determining the frequency of replacement, and investigating the use of biomass-derived feedstocks for the hydrogels. They also aim to explore whether the yeast can capture other contaminants, such as PFAS or microplastics.

“Moving forward, this technology can target other trace contaminants of emerging concern,” Stathatou says. “We see this as a technology with extensive future applications.”

By Impact Lab