Can astronauts make yogurt directly on the ISS?

A growing population on the planet, the need to find new resources… with our summer series “Eating Tomorrow? Explore how we will be led to rethink our diet. On Earth, some focus on insects, and artificial meat … But, and in space? Welcome to the ISS.


Staying healthy is, not surprisingly, a very important goal. This is the case on Earth… and a fortiori in space. However, without the common resources found on our planet, creative solutions must be explored to allow astronauts to carry out their missions – especially on board the International Space Station (ISS), where they can stay for months.

Food is at the heart of this problem and an experiment, designed in Australia (and run through a NASA facility in the US), is currently underway on the ISS to make… yogurt. A choice, we’ll see a little later, that is not anecdotal. NASA also has many projects around this food problem.

Researchers at Swinburne University of Technology are interested in the nutritional value of yogurt made in space. The findings could provide insight into how best to help astronauts during long-duration space flights and missions.

A sensitive gut microbiota

An important factor in human health is the overall health of our gut microbiota, which is estimated to be home to 100 trillion bacteria.

Maintaining the health and diversity of the bacteria within us may be more important in space than on Earth. In fact, in 2019, NASA released groundbreaking results from a year-long study by astronaut twins Mark and Scott Kelly.

In 2016, Scott spent 365 days on the ISS while Mark was on Earth. A fascinating finding from the study was that Scott experienced significant changes in his gastrointestinal microbiota while in space—changes that did not last after returning to Earth.

In 2016, twins and astronauts Mark and Scott Kelly participated in a study on how living in space can affect the human body.
Robert Markowitz/NASA

The theory is that the changes in microbiota experienced by astronauts are due to a lack of exposure to the “everyday” microbes we encounter on Earth. Also, in space, astronauts are exposed to low gravity and high levels of radiation (which increases as they move away from the protection afforded by our planet).

Understanding how to maintain good gut bacteria in astronauts and preserve their health is one of NASA’s current research goals. The American organization is studying this question, in particular, using probiotic capsules and simulated gravity tests. But the results are still not completely satisfactory.

And yogurt?

A yogurt is made by bacterial fermentation of milk. The lactic acid produced during this process acts on the milk proteins to produce the characteristic tangy taste and thick texture of yogurt. We wanted to see how this fundamental process was affected in the space environment.

The new experiment thus conducted is to determine whether different strains of lactic acid bacteria can be used directly in space to make yogurt and cure it. located in the usual place for changes in their microbiota that astronauts experience.

The ideal result would show that healthy, live bacterial cultures could be created from bacteria sent into space and frozen dairy products. This has not yet been realized, although curds have previously been made from bacteria sent from space.

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This would be extremely beneficial for long spaceflights, where fresh food is limited and conventional probiotic capsules lose their effectiveness. Yogurt also provides nutrients to the milk that feed the bacteria.

For the 2021-22 experiment, students and researchers had five milliliter flasks in which they created prototype experiments for the ISS (sent into space as part of the payload available to Swinburne/Rhodium Scientific). All were designed with the aim of studying various probiotics, lactic acid bacteria and yogurt and their behavior and development in space.

The research was notably carried out in collaboration with students from Haileybury School in Victoria as part of the SHINE program (which has already sent human teeth, chia seeds and magnetic fluids on board the ISS) and the Swinburne Youth Space Innovation Challenge (SYSIC).

In 2021, a team from Viewbank College has already studied the effect of magnetic fields on plant growth in space. Pictured (left to right): Tarney Jones, Belle Shea, Madeleine Luvaul and Paisley Noble.

ISS on board

Once ready for flight, samples of the bacteria were prepared and frozen by rhodium scientific teams at the Kennedy Space Center in the US for testing.

Test samples were prepared at the Kennedy Space Center (left), subjecting them to the rapid rotation process (right).
Rhodium Scientific

33 spacecraft were boarded by SpaceX’s Crew Dragon 24 to the ISS and launched on December 24, 2021. Once on board, the samples were taken out of the freezer by astronaut Marc Vande Hey and set aside in a room-temperature test chamber. Japanese experiment module, called Kibo.

After a delay of 48 and 72 hours (the time required for curdling in the earth), the samples were refrozen to determine the degree of progress of the microbiological reactions. It was hoped that the process of converting dairy products into curd had at least begun.

The samples return to Earth at the end of January 2022 and are being analyzed.

The rhodium probiotic challenge samples were flown aboard the SpaceX Crew Dragon 24 spacecraft.

Long awaited results

So far, six different strains of bacteria have been studied (viz Lactobacillus acidophilus), either mixed in various combinations or grown singly. Thanks to space experiments and control experiments on Earth, we will soon be able to determine how much the reduction of gravity and preparations for space travel have affected them.

Among the types of analysis deployed, we use DNA sequencing to detect and characterize any variation in the genetic makeup of bacteria. We will also study the number of generations (or cell divisions) that have occurred in the samples. In addition, bacterial growth media were also investigated. The tests were actually designed to test two types of milk, dairy and “non-dairy”. This is to see potential differences in nutritional outcomes.

But perhaps the most exciting analysis will be the final taste test — along with, perhaps, the discovery that space yogurt is truly out of this world.

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