Breaking down the microbiology world one bite at a time

A yeasty alternative to feeding austronauts

Written by

Manasvi Verma

Imagine yourself aboard the International Space Station. It’s time for dinner and you’re starving. What does your meal look like? If it were 1961, which is when Yuri Gagarin became the first person to eat in space, your food would mostly appear in tubes, in paste-form. Think beef and liver paste for dinner and chocolate sauce for dessert. Thankfully, today’s astronauts have it a lot better than Yuri. With advanced food processing and packaging technology, astronauts can eat similar foods in space as we do on earth. Think fresh fruits, meat, dairy, nuts, coffee, and tea. Doesn’t sound too bad, does it?

In terms of short-term satiety, the current system works great. But it is not self-sufficient and sustainable. Food must be delivered refrigerated or dehydrated to the ISS every 90 days. This poses a challenge for longer space ventures such as returning to the moon, visiting asteroids, or traveling to Mars. These long-term missions will require an autonomous system that is independent of initial launch cargo and resupply from the Earth. The authors of a recent perspective piece in Nature Communications explore a potential new system that uses bioengineered microbes to feed astronauts in space!

When space missions get longer, the demand for food increases. Instead of relying on transporting food regularly, the ideal food system would produce nutritious meals on demand, with minimal input and reduced physical footprint. Thus, microbes are a great candidate for this system since they grow rapidly with minimal input and can be genetically modified. Not only that, but we have also been consuming microbes for millenia in our yoghurt, milk, and our bread. So, we know it’s safe! The authors posit our favorite fungus, Saccharomyces cerevisiae, popularly known as bakers yeast, as a potential candidate. Yeast cells are highly nutritious, contain all the essential amino acids that we need for survival, are fast-growing and genetically tractable. This implies that we can modify yeast to serve our needs of space food. For example, yeast does not have the fat content required for a healthy diet, but bioengineering allows us to tweak these levels (Figure 1B).

This means that we can tailor yeast to have the right nutritional profile, so astronauts are fed a balanced diet. But there is more to consuming food than just nutrition. If we were given the same plate of nutritious mush every single day, we would get tired of it and not want to eat it at all. Menu fatigue is a real problem for astronauts and making sure that there is variety in taste, texture, aroma, and color would help sustain a healthy diet. How can we make yeast appealing?

The authors propose developing a yeast strain collection that has varied textures, tastes, aromas, and colors. For example, yeast has previously been engineered to produce the aroma of raspberries, vanilla, as well as meat by changing the chemicals that the yeast can produce. For texture, yeast has been engineered to produce cellulose, starch, collagen, and gelatin, all of which impart different textural profiles. An appealing color can be generated using engineered pigment genes. For example, carotenoid genes can produce yellow-red colors. It will be important to manipulate multiple genetic pathways at once to impart the ideal taste, texture, and color profile to the yeasts which can be achieved using synthetic chromosomes (Figure 1A).

Say we now have yeast-based food that smells good and looks appealing. The final question is, what is its consumable form? Is it in paste form like Yuri got it or can it be manufactured to resemble Earth-food? The authors further propose using 3-D printing technologies to mimic the appearance of vegetables or meats or into new types of food products (Figure 1D). If the current food system in space is reimagined like this, it would allow for a sustainable, highly customizable, and self-sufficient food production system that appeals to astronauts, keeps them healthy, and minimizes the harm that befalls the Earth with increased agricultural pressure all at once.