According to the data from the Chinese Lunar Palace-1 experiment, each astronaut will consume 3077 g oxygen, 618 g food, and 836 g water per day. Male average daily energy consumption is about 2600 kcal, while female energy consumption is between 1600 - 1700 kcal. That is a huge amount of cost, and humans cannot live without energy, so food supply is obviously at the top of our list of needs for Mars exploration. However, there is a limit to how much food a spacecraft can carry at one time, and sustainable food production is essential to living on Mars for a long time. Our project provides a platform for microbial production, through genetic modification to increase the robustness of the microbial symbiosis system to meet long-term stability. In practical implementation, reasonable fermentation containers for microbial production are necessary, so combined with our hardware design, we proposed a pioneering "Separate-Immobilized" fermentation pattern. Through suggestions from the professor of Guizhou Academy of Agricultural Sciences and the senior engineer of MENGNIU Dairy, we have preliminarily established our final product form, and our partner BUCT-China also provided us with another choice of potential product form.
Due to the compatibility and universality of our project itself as a production platform, the end users would be divided into several dimensions. The first, and most important end users we expect are the settlers on Mars in the future. Since such an end user still exists in the conception of the future, all current researchers concerned with the direction of space migration and the general public interested in space travel are potential targets for us. In the promotion of the project and the investigation of human practice, we have asked relevant scholars and the public for their opinions on the energy consumption of astronauts, artificial ecosystems in space, and space biosafety, and received positive feedback. One day in the future, when humans land on Mars, we hope MBCS-Mars could utilize very little space and equipment support in the Mars bases to sustainably produce food to satisfy the energy needs of settlers. After the initial period of Mars colonization, the resources are gradually abundant, and the equipment is gradually complete, the production platform could expand its range of products to provide other products such as medicine and clothing.
Secondly, this autotrophic sustainable production platform, which does not require external energy input, also has a good application prospect on Earth. Another end user of our project is all current manufacturers wishing to use synthetic biology methods for microbial production. The manufacturer only needs to introduce the existing production chassis microorganisms into the system, and then provide a little power to maintain the operation of the fermentation equipment. In this way, they could realize the production of the target product with almost zero carbon emission, zero energy consumption, and zero pollution, which is considered a low-cost and environmentally friendly production solution.
Lastly, all the future iGEM teams could be our end users. They could involve our symbiotic system in their project to achieve the purpose of engineering microorganisms to work continuously without an external energy supply. In the process, we expect that future teams will give feedback and suggestions for improvement on MBCS-Mars, and even launch new versions of our project by engineering success.
Although our project is aimed at the future, there is no shortage of end users in the present and on the way to the future. We hope that our project can be utilized and enhanced by these potential end users so that the future we hope for is more likely to be realized.
The MBCS-Mars is implemented in fermentation containers in Separate-Immobilized Fermentation. "Separate" means different engineered microorganisms ferment in separate fermenters, and "Immobilized" means microorganisms are immobilized into the medium as the stationary phase, and the culture fluid can flow between microorganisms as the mobile phase. Besides, we introduced hardware design including temperature control, flow rate control, gas control, and solution condition monitoring to the system. To see more details on the hardware design, please go to the Hardware page.
In the original design, microorganisms were immobilized into calcium alginate gels. In practical operation, the steps are as follows:
Loading of immobilized cells
Harvest of products
For the product in solution:
For the product in cells:
After the production of S. elongatus and A. caulinodans, the solution in the device is rich in nutrients, which is ready for the subsequent pre-culture of microorganisms. This is how this system can achieve sustainable production. The protocols for Immobilizing the microorganism cells and releasing the immobilized cells can be seen on the Experiment page.
The immobilization of microorganisms and the release of immobilized cells remains a complex operation. Modularization has been always considered a core idea in iGEM. Therefore, we proposed a photo-controlled plan to efficiently replace fermentation microorganisms.
In the investigation, a reversible bacteria-material adhesion based on photocontrol protein has attracted our attention. The reversibility depends on a pair of light-controlled protein magnets, pMag and nMag, which exist as monomers in the dark and undergo rapid heterodimerization when exposed to 480nm blue light. The reversible adhesion can be achieved by displaying pMag on the surface of microorganisms and Reversible adhesion of engineered bacteria can be achieved by displaying pMag surface on engineered bacteria and modifying nMag on the surface of stationary-phase material under blue light control.
This photo-controlled design allows us to efficiently replace microorganisms of different fermentation products in the same fermenter to save time and space. At the same time, the intracellular product can be harvested efficiently from the reaction vessel. In practical operation, the steps are as follows:
Loading of immobilized cells
Harvest of products
For the product in solution:
For the product in cells:
All the chassis microorganism strains involved in MBCS-Mars are from Risk Group 1 and covered by the White List, so they would do little harm in practical operation. In addition, the immobilized fermentation pattern allows microorganisms to be easily harvested and processed, reducing the risk of outmigration and heavy contact with humans.
In addition, considering that our project is a new scenario, we hope to understand the possible biosafety impact of MBCS and take corresponding measures to minimize the impact. Therefore, we have reached a cooperation with SJTU-BioX-Shanghai, hoping to understand the current situation of biological safety in space in the eyes of the public and make some design improvements and popular science education for it. Through questionnaires and interviews with experts, we learned about the hidden troubles and some corresponding solutions in the microbial culture under different star scenarios. To see more details on our biosafety research results, please go to the Human Practice page.
In terms of implementation, we still have a lot of things that are not perfect. Such as the complete design of the fermenter and digital control system, the hardware and digital design of the photo-control system, and the laboratory verification of light-controlled protein magnets. In the future, we hope to complete the above work and launch a prototype of the fermentation device for trial production.