Every day, astronauts aboard the International Space Station (ISS) conduct experiments that deepen our understanding of the universe. However, occasionally, they also carry out missions funded by private companies — not for personal gain, but to support the space agencies they serve. One such mission, sponsored by sake brewer Asahi Shuzo, aims to create the first-ever bottle of sake brewed in space.

While it may sound like a publicity stunt, this endeavor is a legitimate scientific experiment. The outcome is uncertain, and no one knows if brewing sake in microgravity will actually succeed.

Fermentation in microgravity

Sake is a traditional Japanese alcoholic beverage made from fermented rice, crafted through a precise process involving four key ingredients: rice, water, yeast, and koji mold (which helps convert rice starches into fermentable sugars). Sake plays a central role in Japanese culture, used in ceremonies, festivals, and daily life, and is enjoyed in a variety of settings.

It’s not easy to make sake, however. Here on Earth, fermentation relies on a delicate balance of temperature, gravity, and microbial activity. In space, microgravity presents unique challenges.

Gravity influences how heat is distributed in fluids, which in turn influences the fermentation process. Without gravity’s steady pull, heat transfer may behave unpredictably, potentially altering the flavor, texture, and alcohol content of the sake. Souya Uetsuki, the lead brewer on the project, acknowledges the uncertainties: “There is no guarantee of 100% success for the fermentation tests.”

Dedicated brewing equipment is currently being prepared to be launched to the ISS, where astronauts will mix the ingredients manually in the Kibō Japanese module on the ISS. The module has a controlled environment for this type of experiment, and the process will be closely monitored from Earth.

Yet, the astronauts themselves won’t be the ones drinking the sake. At least, not this time.

Lunar brewery

All this will produce only 520 grams of moromi, or fermentation mash. This moromi will then be frozen and returned to Earth, where it will be pressed and turned into Japanese sake. This is the regular sake-making procedure.

After samples are extracted for analysis, the end result from this process will be a single, 100 ml bottle. That bottle will be sold as “Dassai — Moon Space Brew” for a price of 100 million yen, or around $650,000.

The concept of sake brewed beyond Earth may sound like science fiction, but Asahi Shuzo says their vision is grounded in science and a long-term outlook. The experiment is designed to explore how fermentation behaves in space and how these insights might one day enable brewing on the moon.

On one matter the company is quite right. There’s definitely interest in having a permanent or semipermanent scientific base on the moon. Space agencies like NASA, the European Space Agency (ESA), and Japan’s JAXA are actively working on plans to return humans to the lunar surface with initiatives such as NASA’s Artemis program, which aims to build the Lunar Gateway space station and a sustainable moon base.

Whether or not brewing alcoholic drinks will play a part in these missions, however, is less certain.

Sake in Space

If something really makes astronauts more comfortable, then it’s definitely worth considering, as lunar missions will be extremely taxing. But would we really invest the very limited resources of a moon mission into brewing alcoholic drinks? Even if the answer is ‘no’, the sake company envisions a future where even tourists eventually go to the moon, and they would enjoy a cup of sake.

“In a future where humans can freely travel between the moon and Earth, some will visit the moon as tourists. This project aims to create sake that can be enjoyed on the moon, allowing visitors to have delightful moments there,” Uetsuki said.

In a more pragmatic view, this will provide valuable insights regarding fermentation in microgravity. Fermentation isn’t only for drinks.

“Many Japanese foods, such as natto and miso, are fermented, and this technology could expand into these areas,” Uetsuki said.