On September 19, 1991, two German mountaineers discovered a body emerging from the ice in the Tyrolean Alps, on the border between Italy and Austria.
What initially appeared to be the corpse of a modern climber turned out to be Europe’s oldest known mummy.
This Copper Age man, who died 5,300 years ago with an arrow lodged in his left shoulder, was named Ötzi — after the Ötztal Valley where he was found — and has never stopped surprising scientists.
The latest discovery is perhaps one of the most astonishing: his body hosts live yeast, which a team of researchers recently used to bake sourdough bread.
The finding, published on June 3 in the journal Microbiome, is the result of a comprehensive analysis of the mummy’s microbiome — the body is preserved at the South Tyrol Museum of Archaeology in Bolzano at 21°F and 99% humidity.
Researchers from the Eurac Research Institute for Mummy Studies set out to map the full range of microorganisms living in, on, and around the body — determining which microbes originally belonged to Ötzi, which arrived after his death, and which were introduced during decades of conservation work.
Four Cold-Adapted Yeasts, Active After Millennia
To collect the samples, the team obtained permission from the museum to partially thaw the mummy in April 2019 for five hours, keeping it at 39°F.
They collected ice fragments from around the body, meltwater, surface swabs, and internal samples — along with sediments from the original discovery site and archival samples taken in 1992 and 2010.
Notably, the team identified four cold-adapted yeast strains typically found in extreme environments such as the Alps or Antarctica.
Their presence in the intestines, skin, and meltwater was unexpected. Genetic analysis showed that their DNA had sustained damage comparable to that of other microbes known to have been part of Ötzi’s original gut microbiome. This suggests that the fungi colonized the body shortly after death and have remained there ever since.
By comparing the 2010 and 2019 samples, researchers confirmed that one strain, Glaciozyma, had grown to dominate the population, indicating that the mummy’s microbial ecosystem is not static.
Some outside experts urge caution. Researchers not involved in the study note that without RNA evidence — which would indicate that the yeast genes are active — they cannot rule out that the yeast lay dormant or was reactivated during the thawing process.
However, the Bolzano team argues that the shift in composition between the two samples points to actual metabolic activity.
Three Months of Trial and Error to Make a “Very Good” Sourdough
Once the yeasts were isolated, the next question was obvious: could they be used for fermentation?
The researchers cultivated them in a refrigerator, then put them to work in the kitchen.
It didn’t work at first, but after three months of trials, they produced what they called a “really very, very good” sourdough.
The implications reach far beyond mere curiosity.
Yeasts that ferment at low temperatures — in a refrigerator or even during refrigerated transport — could cut energy use in food production, since they need no added heat to ferment.
The team’s next experiment targets another beloved product of fermentation: beer.
The study also surfaced an unexpected finding. When the mummy was first discovered, the initial recovery team applied phenol to prevent fungal growth.
The newly discovered yeasts can break down this chemical compound, suggesting a potential application in remediation of phenol-contaminated environments.
A gut bacterium virtually absent in modern industrialized populations also turned up in the data — still present in some communities in Africa and South America, and in ancient stool samples recovered from a salt mine in Hallstatt, Austria.
This finding underscores Ötzi’s importance as a rare window into human biology from five millennia ago.
The study’s conclusion is clear: Ötzi is not a static relic. He is a dynamic biological system — one that changes, interacts with its environment, and, apparently, is still fermenting.
