Preparation for the ARTHROSPIRA-C space flight experiment – Insights from ground tests

Jana Fahrion, Cécile Renaud, Ilse Coninx, Wietse Heylen, Claude-Gilles Dussap, Natalie Leys

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Abstract

One of the biggest challenges for the future of human space flight is the reliable and sustainable air, water and food production. Future bioregenerative life support systems (BLSS) aim to overcome these challenges using bioreactors for waste treatment, air and water revitalization, as well as food production. The MELiSSA BLSS developed by the European Space Agency (ESA) uses, besides higher plants, the edible cyanobacterium Limnospira indica (aka Arthrospira/ spirulina) for air revitalization and as an additional food source. The use of L. indica in space will require specific culture conditions which are not commonly used on Earth. These are tested in the precursor space flight experiments ARTHROSPIRA-B and -C (ArtB and ArtC) of which the latter is planned to fly in 2024 to the International Space Station. In the ArtC flight experiment, L. indica is cultured in small-size photobioreactors (Redwire, BE, 50 ml culture volume) which are controlled by light-limiting conditions, meaning that light intensity is the parameter by which the production of oxygen and biomass is controlled. The start-up of the four bioreactors in space includes a start-up of the dormant inoculum (in dark and cold) and propagation in batch mode. Thereafter the photobioreactors are run in semi-continuous mode at 33°C and low light intensities (45-55-70 and 80 μE m-2 s-1) to induce slow oxygen and biomass production allowing longer exposure to space conditions (e.g. cosmic radiation, microgravity) while demanding low amounts of resources such as energy, medium and crew time for feeding. Before the ArtC space flight experiment gets its final acceptance for space flight, the reliability of the set-up is tested via a science verification test (SVT). Here we report on the results of the 2 SVTs performed for ArtC, in 2022 and 2023, using the 4 ground model reactors (GMs), in a laboratory set-up on ground. The 4 GMs were kept successfully operational for 9 weeks continuously, and data were retrieved from all 5 steps, (batch and the 4 semi-continuous cycles (45-55-70 and 80 μE m-2 s-1). The photosynthetic quantum yield was in the nominal range of Limnospira indica PCC8005 (0.30-0.45), and confirmed active photosynthesis in such a space bioreactor setup, providing biocompatible and non-toxic culture conditions. The oxygen production (based on pressure data) was between rO2 (mmol O2.L-1.h-1) = 0,20 – 0,40. Each step to higher light intensity, was followed by higher oxygen productivity, for the first 3 cycles (45-55-70 μE m-2 s-1), in all 4 GMs. In total, ~ 3.76 liters of pure oxygen were produced over the experiment time of 9 weeks. The biomass production was monitored via optical density, and even though the obtained data showed high variability due to calibration and sensitivity limitations of sensors, all reactors produced and maintained acceptable biomass concentrations of 1-2 g dry weight L-1 from start to end. The Oxygen Production Efficiency (Yield of Oxygen per biomass dry weight) was between YO2/X (g.g-1) = 0.43 – 1.15. Out of 4 reactors, 3 were started and maintained fully axenic over the entire experiment length of 9 weeks. Proteomics analysis of the RNA later samples retrieved after each cycle (-80°C) mainly showed differentially expressed proteins related to the photosynthetic pathway. In summary, the SVT showed a successful biomass and oxygen production and the data retrieved are of high value to serve as a baseline for the ArtEMISS-C space flight.
Original languageEnglish
Number of pages1
StatePublished - 24 Sep 2023
Event2023 - EANA Conference - Universidad Carlos III de Madrid-Puerta de Toledo Campus, Ronda de Toledo, Madrid
Duration: 19 Sep 202322 Sep 2023
https://eventos.uc3m.es/92123/detail/congreso-eana-european-astrobiology-network-association-2023.html

Conference

Conference2023 - EANA Conference
Country/TerritorySpain
CityRonda de Toledo, Madrid
Period2023-09-192023-09-22
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