Yeast not only causes fermentation—in some cases, the microorganisms can actually purify water. Even if MIT researchers didn’t know exactly how the process worked, the results were plain to see. Thanks to biosorption, yeast cells bind and absorb heavy metal ions like lead, even at concentrations below 1 part per million. And according to their calculations, a single brewery in Boston could produce enough waste yeast to treat the entire city’s water supply.
With the addition of UV light, the PEG combined into roughly half-millimeter, semipermeable exterior capsules around the yeast cells. Even within their new casings, the waste yeast still removed trace lead from water as quickly as it did on the barrier. “These capsules are porous, so the water can go into the capsules and the yeast are able to bind all of that lead, but the yeast themselves can’t escape into the water,” Gokhale continued.