The oldest cheese in the world may explain the origin of kefir – 09/28/2024 – Science

In the 1990s, Chinese archaeologists were excavating the Tarim Basin, a desert region in Xinjiang, when they found dozens of mummies dating to around 3,500 years ago. In the Xiaohe tombs, as the archaeological site is called, mummies were buried with curious objects around their necks. Ten years ago, it was identified that they were pieces of cheese made with kefir. Now, an analysis of the DNA of bacteria present in the world’s oldest cheese suggests a new hypothesis for the origin of kefir.

The study published last Wednesday (25) in the scientific journal Cell found Lactobacillus bacteria in the old cheese material. Analysis of bacterial DNA indicates that the origin of the bacteria is the Tibet region, which challenges the belief that kefir originated in the Caucasus Mountains, where Russia is today.

Currently, there are two groups of bacteria, one from each region. The Russian type is still used today in the United States, Japan and European countries in the production of yogurt and cheese.

Kefir is a type of fermented milk drink, made from kefir grains, which are colonies of bacteria and yeast. The cheese found with Chinese mummies was made from this milk, indicating that ancient people from the Bronze Age already consumed and applied the fermentation technique in their diet and eating habits.

“It appears that the Xiaohe people actively adopted animal husbandry and kefir cheese became an important part of their culture,” says paleogeneticist Qiaomei Fu, author of the article published in Cell and director of the ancient DNA laboratory at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, in an interview with Sheet. “Subsequently, fermented production spread further across mainland East Asia.”

This shows, according to the researcher, that ancestors used their wisdom to apply and domesticate microbes in the production and conservation of fermented foods, which promoted technical-cultural exchanges and also influenced the evolution of microorganisms.

The Chinese group discovered that the cheeses were made with cow’s and goat’s milk. Interestingly, the study points out that the Xiaohe people did not mix the two types of milk, which indicates a different practice from that which occurred in cheese production in the Middle East and Greece. The reasons for them using a different technique are still unclear.

The sample was kept with the group of scientists for more than a decade, as there was not enough technology to reveal its complete composition. “We designed specific probes to extract the genomes of Lactobacillus kefiranofaciens“, says Fu. His team found the species Lactobacillus kefiranofaciens and Pichia kudriavzeviicommonly found in modern kefir grains.

However, after obtaining the data through genetic sequencing techniques of the mitochondrial DNA of bacteria, comparative analyzes were carried out between ancient and modern species of microorganisms. The study points out similarities between them, but differences in some functionalities and suggests three trajectories in adapting the L. kefiranofaciens.

First, adaptation to environmental stresses, such as the emergence of drug resistance genes and mechanisms in modern strains. Secondly, the reinforcement of defense mechanisms and, thirdly, adaptations to the human intestinal environment. “Modern strains have gained clusters of genes that potentially interact with the host’s gut, which is likely a result of their long-term interactions with humans,” explains Fu.

In interaction with human organisms, the microorganisms in kefir grains participate in the synthesis of nutrients and the elimination of toxins. “Fermenters played an important role in the daily lives of ancient humans, and they propagated these microbes for thousands of years without even knowing about their existence”, comments the paleogeneticist.

The spread of dairy fermentation technology was largely accompanied by human migration and interactions, says Fu, which drove the evolution of lactic acid bacteria. “The separation of the two lineages of L. kefiranofaciens It is probably the result of the dispersion of their common ancestor, initially domesticated in different populations”, says the researcher.

The group aims to further process biological samples from the world’s oldest cheese, such as dental calculus or fossilized fecal traces, and use microbial genomes to investigate past human activities. Scientists hope to reveal lifestyle habits, health and adaptations to the environment of both ancestors and microorganisms themselves.