Would you eat it? Scientists baked bread using yeast found in 5,300-year-old mummy's gut

Scientists have discovered yeast which grown in the guts of a frozen mummy called Oetzi the Iceman for thousands of years. The grown yeast was used by scientists to make a tasty sourdough bread. Oezti died over 5,300 years ago, before the Egyptian pyramids were built, when he was moving aimlessly through the Alps on the border of Austria and Italy, after he was killed by an arrow in the back.

His body remained trapped in ice for thousands of years until two German hikers discovered the naturally mummified remains in 1991 in the northern Italian region of South Tyrol. Since its recovery, the mummy has been well-preserved at a constant temperature of minus six degrees Celsius, matching the conditions of its original icy resting place.

The exceptional state of preservation has enabled researchers to gain unique insights into prehistoric human life through the study of Oetzi, often referred to as the Iceman. In their latest findings, published on Wednesday in the journal Microbiome, a team of researchers based in Italy reported evidence that both ancient and contemporary microorganisms remain active within the frozen remains.

"What we didn't expect to find was yeast," lead study author Mohamed Sarhan of the Eurac Research institute in the Italian city of Bolzano told AFP. The study identified four species of cold-adapted yeasts in samples taken from Ötzi's intestines, skin and the brownish meltwater produced when parts of the mummy were temporarily thawed for examination.

Because these yeasts are typically found only in extremely cold environments, such as Antarctica, researchers believe they entered the body after Oetzi's death. Genetic analysis showed levels of DNA degradation similar to those found in the original gut microbes, suggesting the yeasts colonised the remains relatively soon after death, according to the researchers.

"These yeasts have accompanied Oetzi on his long journey through the millennia," study co-author Frank Maixner said in a statement. Later, the scientists have reproduced the gut yeast in a fridge. "If you tell anyone you have yeast, they immediately ask: Can we use it for bread?" Sarhan said. So they tried to make a sourdough loaf. "Initially, it didn't work," the microbiologist admitted.

After three months of continuous effort, "we had a very, very good sourdough," Sarhan claimed with a laugh. When asked about the scientists' consideration over the use of yeast to brew beer, he responded, "It's on the list."

Yeast breaks down chemicals

The research also highlighted potentially significant practical applications for the yeast. After Oetzi's discovery in 1991, the mummy was initially handled like a conventional human body, and a chemical known as phenol was applied to prevent fungal growth. Researchers found that the cold-adapted yeast was capable of breaking down phenol, raising the possibility that it could one day be used to help clean up environments contaminated by the chemical.

The same bacterium has also been identified in 3,000-year-old human faeces preserved in a salt mine in Hallstatt, Austria, one of the few other sources available for studying ancient human gut microbiomes. Researchers noted that both Ötzi and the Bronze Age miners are believed to have consumed diets rich in fibre and whole grains, unlike many people today.

The same bacterium has also been identified in 3,000-year-old human faeces preserved in a salt mine in Hallstatt, Austria, one of the few other sources available for studying ancient human gut microbiomes. Researchers noted that both Ötzi and the Bronze Age miners are believed to have consumed diets rich in fibre and whole grains, unlike many people today.

The study concluded that the Iceman should not be viewed as a biologically static "time capsule" but rather as a dynamic ecosystem hosting a variety of microbial life. However, researchers cautioned that it remains unclear whether the newly identified yeast poses any risk to the preservation of the mummy and said further investigation is needed.