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In 2016, the Nobel Prize in Physiology or Medicine was awarded to Japanese scientist Yoshinori Ohsumi for his groundbreaking research on the properties of yeast. This award not only recognized his personal efforts, but also revealed the wide application of yeast in scientific research.

Yoshinori Ohsumi once said: "With the help of yeast, we can answer the most basic and important questions about the nature of life." When we carefully examine yeast, a ubiquitous single-cell fungus, we will find that from the ocean to the land, from hot springs to the polar regions, from scientific research to life, yeast has quietly participated in and influenced the world with its unique role.

It is this ubiquitous nature that gives yeast endless diversity. So far, more than 1,000 species of yeast have been discovered, and they have common characteristics but are also very different. Winemaking is one of the magical uses of yeast - yeast metabolizes to produce alcohol, synthesizes various flavor substances, and together with other microorganisms, produces liquor, beer, wine and other wine products with different flavors.

The magic of yeast is far more than just brewing wine. It is widely present in nature and in our lives, and its uses are far beyond our imagination.

Look at the yeast, everywhere

As a master of survival in nature, yeast can be found in ideal places with rich nutrition, extreme environments with low temperature and lack of oxygen, such as high altitude and extremely cold places, and deep sea at the equator. It can even survive in space.

Yeast can also be used in cosmetics. For example, a cosmetics company discovered the polar yeast "Himone" in the hinterland of the Himalayas, which can survive at minus 80 degrees Celsius. The yeast metabolites are applied to a variety of cosmetics to help people protect their skin and fight aging. In addition, red yeast has been discovered at a depth of 11,000 meters in the Mariana Trench. This unique yeast can be found in polar soils, vegetation, rocks, oceans, glaciers and other areas.

How do yeast survive in these extreme conditions?

Yeast can reproduce sexually or asexually. Faced with extreme conditions, yeast will reproduce sexually to produce "seeds" - spores, and quietly wait for the arrival of spring. They will hibernate and endure until the environment improves, and the yeast with stronger vitality will be revitalized and reproduce a new generation of populations. It is this wisdom of surviving in adversity that reveals the secret of species evolution in nature.

In addition to nature, yeast also exists quietly in our daily lives.

For example, beer can be divided into ale and lager according to different fermentation processes, both of which originated in Europe. Most industrially mass-produced beers and German dark beers are brewed by the lager method. Surprisingly, studies have shown that the wild yeast "ancestor" of lager beer was born in the Qinghai-Tibet Plateau thousands of miles away from Europe.

Although the "ancestors" came from the Qinghai-Tibet Plateau, China, as the world's largest beer producer, has long been heavily dependent on imports of yeast strains. For a long time, there was not a single Chinese native strain in the commercial beer yeast strains. Among them, the French Lesaffre Group and the Canadian Lallemand Group accounted for 90% of the Chinese craft beer yeast market. Faced with this situation, the Chinese scientific research team has continuously conducted research and experiments in recent years, completed the testing of more than thousands of strains, and screened and cultivated more than 10 excellent Chinese native yeast strains, breaking the previous embarrassing situation.

(Saccharomyces cerevisiae under an electron microscope)

Have you ever thought that yeast may also be attached to our clothes? When clothes are not washed for a long time or are not washed thoroughly, clothes are not dried in time after washing, and are placed in a warm and humid room or a closed wardrobe, yeast is likely to grow rampantly. If it is not controlled, it will cause the clothing fibers to be corroded, resulting in discoloration and damage of clothes. In severe cases, it may cause skin itching, redness, swelling, desquamation, and even induce sepsis.

Yeast is a large and luxuriant race, including brewer's yeast, baker's yeast, wild yeast, fission yeast, etc. Each type of yeast has different living habits, scattered in every corner of the earth, releasing gorgeous magic.

The "tall" magician of the microbial world

If the microbial world is regarded as the Earth, then yeast is a country, where more than 1,000 ethnic groups live, the total number is incalculable, and they all work diligently in their respective positions. Yeasts are usually tall, several times or even dozens of times larger than bacteria on average. Yeasts also have different appearances, some are spherical and oval, and some look like sausages, lemons or lotus roots.

Yeasts are powerful. In an oxygen-free environment, they can decompose sugars in juice or wort into alcohol and carbon dioxide, turning sugar into wine. They can ferment sugars in flour to produce carbon dioxide, which expands when heated during cooking, making the steamed bread soft, so they are called the mother of fermentation.

(Saccharomyces cerevisiae under an electron microscope)

Most yeasts are rich in nutrients, and more than half of their bodies are proteins. It is estimated that the protein in 100 grams of dry yeast is equivalent to the protein content of 500 grams of rice, 217 grams of soybeans, and 250 grams of pork. The Germans discovered the nutritional value of yeast very early, and even researched and developed edible yeast during the two world wars. Because it looks like pork and beef, it is also called "artificial meat." Subsequently, many countries followed suit and solved many food problems at the time. Therefore, edible yeast, along with atomic energy and penicillin, are called the "three great achievements" of World War II.

Similar to most organisms, yeasts like to live in groups in a suitable environment and work together, which increases their efficiency exponentially. Sometimes they may even produce aroma like humans secrete "hormones".

There is an interesting story about yeast circulating in Maotai Distillery. During the fermentation, the winemakers will use the appearance of a white layer on the surface of the pile as the standard for entering the cellar, which is called "ant eggs". After research, it was found that "ant eggs" are actually a large number of Pichia yeasts. In addition, when the technical team cultivates Pichia yeast at different temperatures and acidities, there is always a strong grain aroma. After research, it was found that it is the ethyl ester substances they produce, which is also the source of the grain aroma of Maotai round wine.

In the world of microorganisms, the yeast family is full of talents. There are many talented members like Pichia pastoris. They work together in harmony to create intoxicating wine masterpieces. As the holy land of Maotai-flavor liquor, Maotai Town naturally becomes a stage for various yeasts to display their talents.

Yeast in "China's No. 1 Wine Town"

The reason why Maotai Town is known as "China's No. 1 Wine Town" is not only because of its long history of winemaking and unique climate, but also because of its unique local microbial environment. This is one of the core reasons why Maotai Town is not replicable.

Maotai Town is surrounded by mountains on all sides, with three mountains surrounding it and a river flowing through it. The average annual temperature is 18℃, the highest temperature in summer can reach about 40℃, and the temperature in winter will not be lower than 0℃. The temperature difference between day and night is very small, which makes Maotai Town very suitable for the reproduction of microorganisms almost all year round, day and night. The unique geographical environment makes Maotai Town look like a natural fermentation workshop, nourishing the growth and reproduction of microorganisms such as yeast. Coupled with the history of winemaking for thousands of years, the entire Maotai Town is full of microorganisms needed for winemaking.

(Maotai Town)

With a unique microbial ecosystem as the cornerstone, the people of Maotai Town have been exploring for thousands of years and summed up the "12987" sauce wine brewing process. Friends who are familiar with sauce wine know that a notable feature of the sauce wine brewing process is "high temperature", which has become one of the important characteristics to distinguish other types of liquor. In addition to the special yeast types mentioned above, common yeasts in the sauce wine brewing process, such as brewing yeast and aroma yeast, usually have a suitable temperature between 25℃-30℃. Faced with the high temperature of the Maotai Town sauce wine brewing process, how do yeasts survive?

Let's take Guotai Liquor as an example. The koji making temperature can reach above 60℃. Studies have found that the number of yeasts increases from the beginning of koji making when the temperature in the koji room rises, and then gradually decreases, almost extinct in about 25 days, or preserved in a dormant state or partially aged and died. If there is no yeast, there is no way to talk about fermentation to produce alcohol. How does sauce wine brewing solve this problem and make up for the problem of insufficient alcohol fermentation capacity of Daqu?

The solution is to pile up the fermentation. In short, before the fermentation is put into the cellar, the fermented grains are spread out to cool down, sprinkled with koji powder and piled into a cone shape. Studies have found that by comparing the yeast species at the beginning and end of the pile, the yeast species content increases to varying degrees during different rounds of piles, and even increases several times.

Zhou Henggang, a well-known expert in the national liquor industry, and others believe that stacking can trap and reproduce microorganisms and play a role in secondary koji making after studying the stacking process.

(Intelligent brewing workshop of Guotai Digital Wine Group)

A loving family of microbes

Yeast is one of the many microorganisms involved in liquor brewing. Yeast and other microorganisms work together to create a colorful world of liquor. If brewing companies want to produce high-quality liquor, they need to continue to conduct in-depth research, understand the habits of yeast and other microorganisms, and create a suitable environment for their survival.

(Some scientific researchers from Guotai Digital Wine Group)

For example, the establishment of a microbial strain resource library is an important part of microbial research. In 2006, Guotai began to establish a microbial strain resource library, among which yeast has the largest number and variety. At present, Guotai has identified 201 strains of yeast from 13 genera, 25 strains of lactic acid bacteria from 5 genera, and 112 strains of spore-forming bacteria from 11 genera, analyzing the microbial basis behind the quality of Guotai liquor and providing materials for fermentation regulation technology. At the same time, Guotai has also established a winemaking microecological "bacteria system" evaluation system to accurately quantify the relative abundance range of microbial species that play a key role in the brewing process.

Based on the long-term exploration of microorganisms, the Guotai research team has figured out the succession rules of microorganisms in the fermentation process of Maotai-flavor liquor. For example, when Guotai liquor undergoes four rounds of fermentation, Schizosaccharomyces pombe, Zygosaccharomyces bailii, Pichia kudriavzi, Saccharomyces cerevisiae, and lactic acid bacteria are the first to multiply in large numbers, promoting the progress of winemaking. Seven days after entering the cellar, Schizosaccharomyces pombe is far ahead, and at the end of fermentation, lactic acid bacteria become the only dominant species.

Guotai Liquor's research on microorganisms has reached the leading level at home and abroad. In recent years, Guotai's scientific and technological research and development has achieved fruitful results, and the overall technology of many scientific and technological achievements has reached the international leading level. Guotai has always believed that technological innovation is the driving force for the development of the liquor industry and the development direction for achieving comprehensive improvement of the industry.

Yan Xijun, founder of Guotai, lifetime honorary chairman of Guotai Digital Wine Group, chief engineer of innovative productivity, and dean of Guotai Research Institute, once said: "Our core job is to serve as a 'nanny' for these invisible winemaking masters."

Every drop of Guotai Liquor is the joint masterpiece of yeast and other microorganisms. These magical yeasts are everywhere, hidden in the air and living between grains, showing a myriad of changing postures. They are "invisible brewing masters" who, with their powerful magic, turn grain into fine wine, realizing the transformation from raw materials to fine wine.

References:

1. Lü Xin, Chen Youjun, Yu Lin, Chen Yuan, Chen Xueqiang. Research and application progress of flavor functional microorganisms in liquor, Brewing Technology, 2024;

2. Lu Jun, Shan Qimuge, Li Changwen, Peng Xiaopei, Meng Tianyi, Zhou Xinle. Rapid identification of yeast flora and preliminary study on fermentation performance of Maotai-flavor liquor, China Brewing, 2017;

3. Chen Shaoyi, Lang Ying, Qiu Shuyi, Wu Botian, Hu Shenglan, Zhou Hongxiang. Comparison of the microbial community structure and production performance of Maotai-flavor Daqu in different areas, Food Science, 2023;

4. Hu Chunhong, Li Xintao, Lu Jun, Lin Liangcai, Zhang Cuiying, Li Changwen, Ye Zhengliang, Xiao Dongguang. Changes of yeast, enzyme activity and metabolites in the process of fermented grains accumulation of Maotai-flavor liquor, China Brewing, 2024;

5. Yang Qiaowei, Research Progress on Application of Yeast, China Food Industry, 2024;

6. Jiang Hongjun, Microbial succession and action rules during the fermentation process of Maotai liquor, Brewing Technology, 2004;

7. Tan Yi, Yan Pei, Li Bingbing, Ren Tingting, Lu Jun, Yin Xuezhong, Luo Guihua, Zeng Dagang. Research progress on the application of functional microorganisms in Maotai-flavor liquor, China Brewing, 2024;

8. Li Changwen, Xu Yan, Lu Jun, Chen Shuang, Meng Tianyi, Fang Cheng, Feng Haiyan, Du Hai, Wang Fan, He Yingxia, Yan Yan, Wang Lulu, Tang Ping, Xiang Danhua. Study on the flavor characteristics and bioactive components of Maotai-flavor Guotai liquor in the core production area of ​​Maotai Town, Jiangnan University, 2022;

9. Xiong Zishu. Research on Chinese brewing yeast - a record of screening and application of different wine yeasts, Brewing Technology, 2002.