Team:Stanford-Brown-RISD/Description
Our overall project can be broken down into four sub-projects. These are characterized as the following: Mycelium Material & Habitat Development, Mycelium Glue Project, Mycelium Filter Project, and finally the Mission Architecture that ties everything together. Below are the descriptions corresponding to each subproject.
Mycelium Glue
In thinking about the versatile uses of mycelium for both Earth and Mars based applications, it became clear that it would be highly advantageous to have some form of attachment mechanism for distinct pieces of mycelium material. This would be advantageous for several reasons, the first being that larger-scale structures comprised of mycelium could be more structurally sound if made up of adjoined subunits rather than one continuous unit. Modular subunits, perhaps in the shape of bricks, could be grown in parallel to accelerate the process of constructing a large mycelium structure. Another compelling reason to engineer an attachment mechanism for mycelium is the flexibility it would afford individuals in space and on Mars: mycelium can grow in virtually any shape and can grow into 20 cm by 10 cm by 8cm bricks in under two weeks.
In down-selecting different forms of attachment mechanisms, our research group ultimately decided on a bacteria-synthesized, mycelium specific bio-glue. There were several reasons for this decision, the first one being how mass-efficient the system could be made for spaceflight. It’s been estimated that on a journey to mars, the cost of transportation is approximately $2.78 million per kilogram, so transporting bacterial spores would be highly cost-efficient in comparison to several kgs of pre-made glue or larger scale attachment devices [1]. The bacterium Bacillus subtilis has been shown, by our lab group and others, to be highly resilient to the spaceflight environment and would be a viable organism to use for this endeavor [2]. It’s also worth noting that NASA and other space agencies have long been developing applications of bacteria on space; once the infrastructure for these applications are in place, the addition of a singular DNA construct for our bio-glue is an exceptionally minimal burden [3].
Mycelium Filter
Clean water is vital. A self-assembling habitat for extraterrestrial exploration is simply not stable without a sustainable, regularly filtered water supply, and access to clean water remains one of the largest challenges humanity will face in the upcoming future, whether it’s in space or on earth. Another challenge is metal acquisition, whether from waste electronics or martian regolith. We developed a cost-effective, scalable, completely biodegradable filtration system for waste metal recovery from aqueous solution, using copper as a proof of concept. We first modified metal binding domains through computationally-aided rational design, and tested multiple in tandem to increase the binding capacity of our peptides. We then created metal binding domain - chitin binding domain (CBD) fusion proteins, using the CBD as a platform for functionalizing the mycelium surface and enhancing its properties. We quantitatively characterized and modeled the binding affinity of the individual domains to rigorously understand the molecular underpinnings of the filter. We finally created a tangible, functioning prototype composed of filter strips of pure mycelial material that removes >92% of the copper from a >300 μM aqueous solution within 30 minutes through surface adsorption and tangential flow, demonstrating the viability and utility of our novel process for filtration and biomining applications, both on-earth and in space.
Mission Architecture
Mission architecture involves designing and planning a mission.
The goal of our mission was framed around giving other missions feasibility by giving them the ability to work in places that might be too dangerous on the surface by providing a protected environment which our mycelium structure would provide.
The habitat is based around a 3 layered plastic dome, of which the outer layer is a layer of water which will freeze into ice, another shell encloses the cyanobacteria, and lastly the layer of mycelium. Each layer provides its own benefits. The ice water layer will be drawn from a pump which will melt subsurface ice water from our landing site, this layer provides insulation as well as providing radiation protection. Lastly this layer can be partially melted to provide water to our living cyanobacteria and fungus. The layer of cyanobacteria, suspended in a water solution will receive the sunlight which passes through the ice and use this energy it to break down carbon dioxide as well as molecular nitrogen, and create biologically available carbohydrates and nitrogen. We considered a design for a system that would ensure the cyanobacteria was well supplied and that could feed the products into the mycelium matrix. The source of the nutrients required for cyanobacteria growth would in part be provided by the martian regolith as well as the atmosphere and would be supplemented with any lacking nutrients by fertilizer brought from earth. The mycelium layer provides the main functionality in the system, providing structural stability, radiation protection and insulation and can be functionalized to provide additional benefits such as water filtration. The mycelium from the species we used in our experiments as well as many others produces edible mushrooms which astronauts could eat. Our design requires some robotic assembly.
In order for our mission to succeed we have made some assumptions which are based on expert advice in the field. Talking to Planetary Geologist Jim Head, we came to the conclusion that a landing site in the Deuteronilus Mensae portion of Mars would be the most suitable. Deuteronilus mensae is near the equator so there is less seasonal temperature flux. It is still far enough from the equator that it can still recieve ice and dust accumulation and currently there is a strong hope that there is a large body of ice water within 10m of the surface in this area according to Head. The region also has a lower elevation and thus thicker atmosphere which will provide more nutrients and protection to our system as well as helping slow down any lander we send to the area.
References
[1] Folger, J. (2012, August 20). Why curiosity cost $2. 5 billion.https://www.investopedia.com/financial-edge/0912/why-curiosity-cost-2.5-billion.aspx.
[2] Bucker, H., Horneck, G., Wollenhaupt, H., Schwager, M., & Taylor, G. R. (1974). Viability of Bacillus subtilis spores exposed to space environment in the M-191 experiment system aboard Apollo 16. Life Sciences and Space Research, 12, 209–213.
[3] Horneck, G., Klaus, D. M., & Mancinelli, R. L. (2010). Space microbiology. Microbiology and Molecular Biology Reviews : MMBR, 74(1), 121–156. https://doi.org/10.1128/MMBR.00016-09.