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Will astronauts be able to make yogurt directly on board the ISS?

Ever-increasing 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 are looking at insects, and artificial meat… But, and in space? Welcome to the ISS.

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

Food is central to this issue and an experiment, designed in Australia (and conducted via NASA facilities in the United States), is currently underway on board the ISS to make… yoghurts. A choice, we will see a little later, which is not anecdotal. NASA also has many projects in development around this food issue.

Researchers from the Swinburne University of Technology are interested, with this study, in the nutritional values ​​of yoghurt made in space. The findings could provide insight into how best to help astronauts sustain themselves during long-duration spaceflights and missions.

A sensitive intestinal microbiota

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

Maintaining the health and diversity of those bacteria we harbor within us might be even more important in space than on Earth. Indeed, in 2019, NASA released groundbreaking results from a year-long study of astronaut twins Mark and Scott Kelly.

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

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

The theory is that the changes in the microbiota experienced by astronauts are due to the lack of exposure to the “everyday” microbes that we encounter on Earth. Also, in space, astronauts are exposed to less gravity and high levels of radiation (which increase 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 agency is studying this question using, in particular, probiotic capsules and simulated gravity experiments. But the results are not yet fully satisfactory.

And the yogurt?

A yogurt is made by the bacterial fermentation of milk. The lactic acid produced during this process acts on milk proteins to create 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 conducted thus aims to determine whether different strains of lactic acid bacteria can be used to make yogurt directly in space and remedy in situ to the changes in their microbiota that astronauts experience.

The ideal outcome would be to show that healthy, living bacteria cultures can be generated from bacteria and frozen dairy products sent to space. This has not yet been realized, although yoghurts have been made from bacteria sent from space previously.

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

For the 2021-22 experiment, students and researchers had five milliliter flasks in which they built 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 different probiotics, lactic acid bacteria and yoghurts and their behavior and development in space.

This research is notably carried out in collaboration with students from Haileybury School in Victoria as part of the SHINE program (which had already sent human teeth, chia seeds and magnetorheological fluid on board the ISS) and the Swinburne Youth Space Innovation Challenge (SYSIC).

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

On board the ISS

Once ready for flight, the samples of bacteria to be tested were prepared and frozen by Rhodium Scientific teams at the Kennedy Space Center in the United States.

The experimental samples were prepared at the Kennedy Space Center (left), which involved subjecting them to a fast-spinning vortex procedure (right).
Rhodium Scientific

33 vials boarded the ISS via SpaceX’s Crew Dragon 24, and were launched on December 24, 2021. Once on board, the samples were taken out of the cold room by astronaut Mark Vande Hei and placed aside in a room-temperature experiment chamber in the Japanese experiment module, called Kibo.

After the delays of 48 and 72 hours (the time needed to make yogurt on Earth), the samples were refrozen in order to fix the levels of progress of the microbiological reactions. It was expected that the process of transforming dairy products into yoghurts had at least begun.

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

The Rhodium Probiotic Challenge samples were flown on the SpaceX Crew Dragon 24 spacecraft.

Long-awaited results

So far, six different strains of bacteria have been studied (such as 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 reduced gravity and preparations for space travel have affected them.

Among the types of analyzes deployed, we use DNA sequencing to identify and characterize any variation in the genetic composition of bacteria. We will also study the number of generations (or cell divisions) that will have occurred in the samples. In addition, bacterial development media were also investigated. The experiments were indeed 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 that of the final taste test – with, perhaps, the discovery that space yogurt is truly out of this world.

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