Astronauts on board the International Space Station are notoriously thrifty. With limited storage space, and a long trip home to pick up extra supplies, resources must be recycled many times.
A clever life support system controls the atmospheric pressure on board and provides clean water and fresh air to astronauts. Filtration systems convert waste water from showers, urine and even sweat into drinking water, while carbon dioxide scrubbers clean up the air for breathing. Some products, however, inevitably go to waste and are ejected into space.
On their much longer journeys, Mars-bound astronauts could see themselves recycling everything (and we mean everything!) to reach the red planet in one piece. Chemical engineer, Mark Blenner has been studying how the microbes that give us bread and beer can help them get there.
Rising to the challenge
Yeast are single celled micro-organisms that have been used by humans for centuries. From brewing and baking to making medicines, yeast is a super-organism.
Yarrowia lipolytica is a particular strain of yeast that can make use of unusual sources of carbon. These cells are specialist builders that link carbon molecules into long chains. They then store them as oils and fats. Blenner hopes to cultivate a space yeast that can act as on-board factories to help replenish essential supplies on the fly.
To grow these flying factories in space, the astronauts must feed it carbon and nitrogen. By using the carbon from their exhaled breath, the team can grow algae as a tasty food source for the yeast. The nitrogen for the yeast would come from the astronauts’ pee, where it is stored as a molecule called urea.
One of the tasks that Blenner and his team have set the yeast is producing essential nutrients called Omega-3 fatty acids. These are naturally occurring fatty acids that we need to help us stay healthy and happy. As mammals, we cannot produce them ourselves and must get them from our diet, eating foods such as oily fish, nuts, spinach and eggs. Supplements have a poor shelf-life and wouldn’t last the trip to Mars. As such, astronauts must find an alternative source of necessary nutrients.
Plastics from pee
As well as supplementing their diets, astronauts could even use their waste to make plastics on board the ship. With trips lasting several years, they will need spare parts to fix any problems. However, every extra ounce adds to the fuel costs needed to leave Earth, meaning they must find ways to reduce, reuse and recycle.
Alongside storing carbon as oils and fats, Blenner’s space yeast also stores hydrogen. Together, they provide the two main ingredients for making bioplastics. With a bit of genetic-tinkering, the super-yeast can be engineered to produce a polyester-like material. This is similar to the plastic fibres we use in our clothing. Once extracted, these could fuel 3D printers, crafting the tools and parts needed to keep the spacecraft ship-shape.
For now, the yeasts can produce only small amounts of nutrients and plastics, and extracting them is proving tricky. The next step will be to boost output, but until then, astronauts will have to make do with more traditional tools!