Looking Into The Future
The AstroYeast Microfarm is a system that consists of two major parts: the AstroYeast and the bioreactor. These two components work together in the goal to provide a platform for biomanufacturing in space.
With major space missions in the relatively near future like our mission to Mars and planned Moon missions, along with the emergence of private space companies, it seems that we as humans are getting closer and closer to having space travel be a more common occurrence. While it may be limited now, the Concordia-Montreal team is looking to the future. We want to help make the next major steps in space travel possible.
Major hurdles to this are the cost to send things into space and the space available on a shuttle. This means that both having a lot of material on a shuttle at a time is impractical when it comes to available space, but also constantly having to replenish supplies with payloads is impractical as well. Our project, the AstroYeast Microfarm, is our attempt to solve both of these problems. If implemented, our system would allow for a reliable means for bioproduction in space. This allows for the production of nutrient molecules, medicine, and other useful molecules such as building materials to be produced. Additionally, this would allow for the production of food, in the form of yeast itself, as we are using baker'ss yeast, a commonly consumed species of yeast on Earth. This yeast can even be fortified with the nutrients it can be designed to produce, such as with vitamin A. However, for yeast to serve as a viable chassis for bioproduction, it has to be adapted for microgravity conditions, which is a challenge that we are trying so solve through lab adaptive evolution with our microgravity simulators.
The production of AstroYeast consists of 3 distinct sub-processes. The first sub-process is that of the setup. It requires crew intervention to inoculate the culture media, verify that the system is well attached and connected, and instruct the system'ss computer to start the production. The setup should not require more than 30 minutes of crew time. Then, the production sub-process can start which does not require any crew intervention. During this week-long sub-process, Astroyeast cells grow and produce the nutrients and flavour molecules required by the crew. It starts with the pumping of the media into the culture vessels using automated pumps and valves. The nutrients produced by AstroYeast in each production cycle are expected to fulfill the crew'ss nutritional requirements for a few weeks up to a few months.
Then, as AstroYeast grow, the temperature, pH, and oxygen and glucose levels are monitored and regulated. To control the temperature, the bioreactor vessels are housed inside a well-insulated incubator. For pH control, small quantities of hydrochloric acid and dissolved carbon dioxide are used. The oxygen levels are controlled using an oxygenator connected to the bioreactor vessels while the glucose levels are regulated through a glucose supply and mixed using the piston system. Once the production is completed, the preparation sub-process can start. It transforms the yeast culture into a delicious yeast spread and is partially automated as it requires some crew intervention. It starts with the drainage of the culture vessels into a storage vessel using the piston system.
During the drainage, the culture media is filtered so that the yeast can be retained in a preparation vessel. The yeast is then washed using water to debitter it. The crew then needs to transfer the preparation vessel to the mixer located in the incubator. This step should take no longer than 15 minutes of crew time. On the mixer, the vessel containing the yeast is heated and stirred for a few hours. Once the preparation is done the yeast spread can be taken out and safely consumed or stored away.
Multiple shutdown mechanisms are implemented to ensure crew safety and conserve energy. Automatic shutdown procedures are in place if anomalies are detected. Manual shutdown procedures that are either electrically or mechanically activated are implemented to give the crew full control of the shutdown. To store the yeast spread, a sealed and sterile container is used. It does not need to be refrigerated and has a shelf life of up to 3 years. To clean and sterilize the vessels, water and high heat are used. The cleaning and sterilization process is fully automated. The incubator can reach the necessary temperature to sterilize the system safely.
AstroYeast Microfarm is very compact and does not require more space than a household microwave. The total crew time required for a week-long cycle is at most an hour which includes storage and maintenance. The automation of the yeast production process provides ease of handling, reliability and increased productivity which is supported by existing research performed by Schuerlein et al. (Schuerlein).
Seeing as one of the major implementations of our project is in food production, it is important to reflect on the product itself and make sure that it'ss palatable. Our product, being a yeast paste such as that shown above, would have a lot of similarities with other yeast products. Our food product is a yeast spread which has a beige colour. It has the appearance of a thick paste, with a consistency similar to that of cream cheese. Its aroma is meaty, cheesy, and nutty, with a caramel aroma when no flavour molecules are specially produced. However, as AstroYeast is designed as a chassis for bioproduction, flavour molecules such as limonene are also produced providing a great variety of aromas. The flavour of the yeast spread is predominantly umami (Biospringer), but will also be quite varied depending on the flavour molecules produced. We could determine which flavouring molecule to synthesize to meet the crew'ss personal preference. The texture of the yeast spread can be described as pasty, a bit thick, and sticky (Njt). It also depends on moisture content.
Sources
S. Schuerlein et al., "A versatile modular bioreactor platform for Tissue Engineering", Biotechnology Journal, vol. 12, no. 2, p. 1600326, 2016. Available: 10.1002/biot.201600326 [Accessed 23 July 2021]
Biospringer. (2019). Yeast Extract A Treasure From Nature For Food. https://biospringer.com/wp-content/uploads/2019/05/biospringer-whitepaper-2019-05-07.pdf
Njt, E., & Om, A. (2019). Produced from Some Selected Tropical Fruits. J Food Process Technol, 10(5), 790. https://doi.org/10.4172/2157-7110.1000790