ARTHROSPIRA-C space flight experiment: Validation of biomass and oxygen production bioprocesses in a space bioreactor prior to upload to space

The Micro-Ecological Life Support System Alternative (MELiSSA) project of the European Space Agency develops a biological recycling loop for manned long-term space flight. The air revitalisation and food production are carried out by vascular plants and a photobioreactor containing the cyanobacterium Limnospira indica . In the space flight experiment ARTHROSPIRA-C, cultures of L. indica are run in a one-week batch mode (45 μmol photons m −2 s −1 ) followed by four semi-continuous cycles of two weeks length. Each cycle has a different, predefined light intensity following an increasing regime (45-55-70-80 μmol photons m −2 s −1 ). In this study, two ground science verification tests (SVT and δ-SVT) were conducted in a laboratory setting to test the reliability and functionality of the hardware- and software of ARTHROSPIRA-C. The SVT explored all four cycles and light intensities and δ-SVT was an additional test where only cycle 1 and 2 were performed. δ-SVT was used to investigate anomalies during SVT. These experiments revealed oxygen production rates between 0.10 ± 0.03 and 0.45 ± 0.01 mmol O 2 L −1 h −1 and biomass production rates between 0.008 ± 0.000 and 0.021 ± 0.002 g L −1 h −1 while demonstrating sustained photosynthetic activity at all tested light intensities. In addition, proteomics analysis revealed light intensity-induced effects on multiple pathways, whereas the lipidomic analysis reported no alterations. This study delves into the ground tests conducted during ARTHROSPIRA-C, paving the way for a forthcoming successful flight experiment scheduled aboard the International Space Station in autumn 2024. • Cyanobacterium Limnospira indica was succesfully cultured over exended durations (upto 9 weeks) in space flight hardware. • The pre-space experiments showed successful storage, revival, batch propagation and production of biomass and oxygen. • The biomass production was in the expected range while the oxygen production was below the expected range. • Proteomic analysis revealed an impact of light flux intensity on the carbon and nitrogen assimilation metabolic pathways. • Lipidomic analysis showed that the biomass lipid composition remained consistent across all tested light flux intensities.