MELISSA (Micro-Ecological Life Support System Alternative) Program — Extra-Terrestrial Ecosystems

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Looking for food that could be harvested by astronauts far from Earth, researchers focused on spirulina, which has been harvested for food in South America and Africa for centuries. ESA (European Space Agency) astronaut Samantha Cristoforetti ate the first food containing spirulina in space and now the knowledge is being applied to a pilot project in Congo as a food supplement. ¹⁾

Preparing for long missions far from Earth, astronauts will need to harvest their own food. ESA's MELISSA (Micro-Ecological Life Support System Alternative) team is looking at creating a closed ecosystem that continuously recycles waste into food, oxygen and water.

Figure 1: Spirulina astronaut food (image credit: ESA)

The Arthrospira bacteria – better known as spirulina – have been a staple part of MELISSA for many years because it is easy to grow and multiply rapidly. The bacteria turn carbon dioxide into oxygen and can be eaten as a delicious protein-rich supplement. They are also highly resistant to radiation found in outer space.

During his stay on the International Space Station, ESA astronaut Andreas Mogensen tested cereal bars containing spirulina collected through MELiSSA's system to ensure they taste good in space.

Figure 2: Researching spirulina (image credit: ESA)

From space to the Congo:

The SCK-CEN (Studiecentrum voor Kernenergie) research center in Mol, Belgium, has been involved since the early days of MELISSA. Their research into spirulina investigated aspects of the bacteria such as gene expression, enzyme activity, how they absorb light, how they move during growth and how they ingest nutrients. This unparalleled knowledge is now being applied around the Congo town of Bikoro.

The staple diet in this region is cassava, which supplies very little protein, so spirulina could supplement the local diet with much-needed protein as well as vitamin A and iron.

Figure 3: Growing spirulina (image credit: ESA)

The pilot phase is looking at growing spirulina in tubs of water with potassium bicarbonate and other ingredients that can be found locally. Under sunlight and regular stirring, the tubs are easy for harvesting and provide for a family of six.

The spirulina is dried and powdered, with 10 grams sprinkled on food each day enough to satisfy most dietary requirements – adding a slightly saltier taste to a dish.

Employees from the SCK-CEN research center are working with local entrepreneurs to help make the system a success after beginning in one village.

And back to space:

Experiments are also planned on the Space Station because nobody knows how some of the organisms in the MELISSA system will grow in space. A series of experiments will fly the Arthrospira bacteria and cultivate them in the Biolab facility in ESA's Columbus laboratory to see how they adapt to weightlessness.

"When we started working on MELiSSA over 25 years ago we were inspired by ecosystems such as found around lake Chad 1500 km to the north of Bikoro," concludes Christophe. "It is fitting that our work creating a circular ecosystem is now helping the local population as well as future astronauts in space."

Figure 4: Artist's rendition of spirulina (image credit: ESA)

Table 1: Some background on the MELISSA space research program: ^{2) 3)}

Designing the MELISSA loop:

The driving elements for the design of an ideal bioregenerative life support system (BLiSS) are: ⁴⁾

1) the production of a highly nutritious biomass and O₂

2) with the direct use of light as a source of energy for microbiological biosynthesis

3) with limited O₂ consumption

4) in an easy to handle compact reactor setup adapted for space flight

5) allowing an efficient and biosafe re-conversion of waste, CO₂, and minerals in simplified recycling steps

6) using known and already studied organisms that (vii) preferably possess a certain degree of ‘space robustness'.

A typical balanced diet contains carbohydrates, fat, and protein as well as a number of vitamins and minerals. Hence, the most important criteria for the nature of the edible biomass are the high production rate and quality of its nutritious compounds. The organisms should equally possess a high rate of O₂ evolution and photosynthetic CO₂ fixation, combined with a limited volume ratio. Cyanobacteria are the ideal candidate organisms as they generally fulfill the above stated conditions. They are a group of evolutionarily ancient, morphologically diverse and ecologically important bacteria, which are able to carry out oxygenic photosynthesis, while using CO₂ as sole source of carbon. They make a significant contribution to the global primary production of the oceans and have become locally dominant primary producers in many extreme environments, like hot and cold deserts, hot springs and hypersaline environments. Among the traditionally consumable cyanobacteria are Arthrospira, the terrestrial cyanobacterium Nostoc commune, and the symbiotic association Anabaena/Azolla. Arthrospira (cf. Spirulina cakes) were grown and eaten in pre-Hispanic Mexico by the Aztecs as "tecuitlatl" and by Kanembu tribeswomen from small soda lakes in the vicinity of Lake Chad as "Dihé" cakes, because of their extraordinary nutritional value.

The main dietary features of spirulines are a very high content of proteins (up to 70% dry weight) with a well balanced aminogram and a high content in vitamins and essential unsaturated fatty acids. In vivo culturing of Arthrospira sp. is easy and very productive. As their growth rate tends to be very high, they are able to produce 20 times more proteins per hectare as compared to soya.

Although trees are the best land plants for absorbing atmospheric carbon dioxide, being able to fix from 1 to 4 tons of carbon per hectare per year, Arthrospira sp. are even more efficient. Research in the California desert with industrially cultivated Arthrospira proved that Arthrospira fixes 6.3 tons of carbon and produces 16.8 tons of oxygen per hectare per year. Furthermore, Arthrospira sp. is very digestive, in contrast to many other microorganisms, notably because of its weak content in nucleic acids and its lack of a rigid cellulose cell wall.

As a consequence, there is no need for cooking or any special treatment before human consumption, allowing for the preservation of the integrity of components like vitamins or polyunsaturated fatty acids. Hence, the easily cultivated food product Arthrospira sp. PCC8005 was selected as the O₂ producer and essential food supplement in the conceptual design of the MELISSA loop (Figure 5). ⁵⁾

In order to provide consumers with all the requirements for a complete diet, a plant compartment, achieving the same goals as the Arthrospira sp. compartment, containing lettuce, red beet, and wheat was added to the loop.

With the choice of Arthrospira sp. and a plant compartment as sources of food- and O₂-producing compartments, the first two conditions for the design of an ideal BLiSS were met. In additional compartments it was necessary to focus on minimal O₂ consumption in simple and compact reactor processing systems enabling efficient and safe waste recycling.

Long-term space missions (e.g., to Mars), including the establishment of a long-term, manned base, implies the development of a reliable life-support system including food supply and waste management. Due to the mission duration, supplying all food, oxygen, and water from Earth will result in a tremendous cost; therefore, the life-support system has to be increasingly regenerative. Presently, on board ISS, technologies are operational to regenerate clean water by appropriate treatments (e.g. SRVK, WRS). However, these techniques generally consume a lot of energy and cannot produce food, which must still be resupplied from Earth. Food production can only be achieved by biological means, and the introduction of biological techniques opens a new set of solutions for other life-support requirements such as atmosphere, water, and waste management. A space-based life-support system must meet the rigid requirements of efficiency, mass, crew time, reliability, and safety. For the design of regenerative systems, for the study, experimental testing, and development of future manned missions, a purely engineering approach has to be followed. For the last 30 years, numerous developments of recycling technologies have been initiated by the major space agencies. However, these typically consist of recycling one product in a new consumable (i.e. water recycling, O₂ production) without a global overview of the complete life-support system. For these reasons, namely overall mass balance and, engineering approach, ESA has initiated the MELISSA project (Ref. 5).

The MELISSA Concept:

Inspired by an aquatic ecosystem, the MELISSA (Micro-Ecological Life-Support System Alternative) project has been set up to be a model for the study of regenerative life-support systems for long-term space missions. ⁶⁾ The compartmentalized structure of the loop and the choice of the several microbial processes has been done to simplify the behavior of this artificial ecosystem and allow a deterministic engineering
approach. MELISSA has five major compartments (Figure 5) colonized, respectively, by thermophilic anoxygenic bacteria, photo-heterotrophic bacteria, nitrifying bacteria, photosynthetic bacteria, higher plants, and the crew.

The project is organized in five phases: 1) Basic R&D, 2) Preliminary Flight Experiment, 3) Ground & Space Demonstration, 4) Terrestrial Transfer, and 5) Education & Communication. As it was not possible to present all activities of these phases, only the major decisions and important results of Phases 1 to 3 are reviewed.

Phase 1 – Basic Research & Development:

For any closed life-support loop , the efficiency of the complete loop is totally dependent on the weakest process. The early days of the project mainly focused on the identification of the proper microbial strains. Early expectations that pure and axenic cultures could be selected for all functions were demonstrated to be impossible. This impossibility was mainly due to two reasons: waste degradation with pure cultures is limited to a few percent of the input stream, and the high percentage of microbial food sources is limited by the nucleic acid content and the associated risk of uric acid accumulation. For these reasons, specific attention has been devoted to the waste- degradation sub-subsystem as well as the food-production subsystem. Parallel activities related to modeling and control, as well as genetic stability, have been pursued.

For more information, consult reference 5).

Figure 5: The compartmentalized structure of the MELISSA loop concept (MELISSA Research Program)

2) "Extra-Terrestrial Ecosystems: The European Space Agency MELISSA Program,The European Biotech News Website, " URL: http://labiotech.eu/extra-terrestrial-ecosystems-the-european-space-agency-melissa-program/

3) "The MELISSA Foundation -Knowledge of regenerative life support systems for long term space missions," URL: http://www.melissafoundation.org/

4) Larissa Hendrickx, Heleen De Wever, Veronik Hermans, Felice Mastroleo, Nicolas Morina, Annick Wilmotte, Paul Janssen, Max Mergeay, "Microbial ecology of the closed artificial ecosystem MELISSA (Micro-Ecological Life Support System Alternative): Reinventing and compartmentalizing the Earth's food and oxygen regeneration system for long-haul space exploration missions," Research in Microbiology, Volume 157, 2006, pp: 77–86, URL: http://tinyurl.com/zvyu27z

5) C. Lasseur, J. Brunet, H. de Weever, M. Dixon, G. Dussap, F. Godia, N. Leys, M. Mergeay, D. Van Der Straeten, "MELISSA: The European project of closed life support system," European Space Agency, TEC-MMG Keplerlaan 1, 2200 AG Noordwijk, The Netherlands, Gravitational and Space Biology , Vol. 23(2) August 2010, URL: http://citeseerx.ist.psu.edu/viewdoc/download
?doi=10.1.1.464.3630&rep=rep1&type=pdf

6) M. Mergeay, W. Verstraete, et al. (1988). "MELISSA - A micro-organism-based model for CELSS (Controlled Ecological Life Support System) development," Proceedings of the 3rd European Symposium on Space Thermal Control and Life Support Systems, Noordwijk (The Netherlands) ESA SP-288, pp: 65- 69
 

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (herb.kramer@gmx.net).

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