PhD Defense | Jana Fahrion | Biological oxygen production and air revitalization for habitats on the Moon

Biological oxygen production and air revitalization for habitats on the Moon

Manned deep space missions to explore our solar system require oxygen, potable water and food as supply for the crew. Bioregenerative life support systems (BLSSs) use bioreactors to recycle waste and spent air to provide these supplies. During the development of BLSS, all technical and biological components are investigated individually, on Earth as well as in space. The work presented here is part of the ArtEMISS project (Arthrospira sp. gene Expression and mathematical Modelling on cultures grown in the International Space Station) and focusses on oxygen and food production in the scope of the MELiSSA (Micro-ecological Life Support System Alternative) project of the European Space Agency. In the scope of ArtEMiSS, a space flight experiment to test the ability of the cyanobacterium Limnospira indica cultures to produce oxygen and biomass in semi-continuous mode in space is scheduled for September 2024 (ARTHROSPIRA-C, ArtC). In this experiment, miniaturized space compatible photobioreactors (PBRs) are used to grow L. indica. The cultures first need to be stored at 4°C in the hardware, brought to the International Space Station, revived from their dormant stage and propagated to a suitable biomass density. Then, the four two-week long semi-continuous experiment phases, which have 4 increasing light intensities (45-55-70 and 80 µmol photons m^-2 s^-1) follow. 

This PhD thesis provides the ground data to perform the upcoming space flight experiment and investigates L. indica under space simulation conditions (chronic low-dose γ-irradiation and simulated microgravity) for the further development stages of the MELiSSA recycling loop, where the PBRs will be run onboard space shuttles on their way to planetary bodies (e.g. Mars). All phases of the planned ArtC space flight experiment were investigated here in detail in laboratory set-ups. Suitable storage conditions to bring the cultures to space before start-up of ArtC were established and the propagation phase of ArtC was investigated by using different combinations of temperatures and light intensities and showed that a low light intensity (35-75 µmol photons m^-2 s^-1) and warm temperature (30-34 °C) are best to reach a high biomass density. 

Chronic low-dose γ-irradiation induced a transient hormesis effect on L. indica and proteomics confirmed that no detrimental effects are to be expected at irradiation doses similar to a Mars transit flight. Simulated microgravity experiments (using the random positioning machine, RPM) revealed oxygen inhibition inside the cultures due to an increase in liquid boundary layer, which resulted in a deficient gas transfer, trapping the produced oxygen of L. indica inside the cultures. High oxygen levels inside the cultures cause a decrease in carbon fixation, because oxygen competes with carbon dioxide at the enzymatic site of RuBisCO. The semi-continuous phases were tested using the ArtC hardware in ground tests. Here, the experimental schedule of ArtC was used and resulted in comparative data for the space flight. These tests have demonstrated the successful production of oxygen and biomass over the full experiment time (5 and 9 weeks), providing essential insights into the reliability of hardware and the active photosynthetic bioprocess within the prototype PBRs. Insufficient gas transfer between the liquid compartment and gas compartment of the PBRs was detected. This causes, similar to the RPM experiments, oxygen inhibition of L. indica and resulted in oxygen inhibited growth kinetics instead of the originally planned light limitation. The pigment production pathways were downregulated (proteomics), a natural response to the increasing light intensities in the four semi-continuous cycles. 

In summary, the knowledge gathered in this work plays a key role in the further development of the MELiSSA loop and leads space research to successful biological air revitalization and food production for manned space exploration.

Promoter:

• Claude-Gilles DUSSAP (Université de Clermont Auvergne)

SCK CEN mentor:

• Natalie Leys

Click here for a list of obtained PhD degrees.