Redesign of a microalgal photobioreactor for space applications in a bioregenerative life support systems perspective

The present thesis focuses on the redesign of a microalgal photobioreactor (PBR) for application in space habitats, specifically reporting the results of the research activities carried out during the traineeship at the STAM S.r.l. facility. These activities contribute to BIOLUNA, a project funded by the Italian Space Agency (ASI) with the aim of developing bioregenerative life-support systems for space missions. The final objectives of the thesis consist of compiling the overall knowledge and data collected within the project and investigating the effects of the proposed design modifications to the STAM PBR, with the aim of ensuring optimal performance within the intended scope. The research activities were centered on the structural and functional optimization of a semi-closed multitubular PBR to address challenges associated with the space environment. First, the PBR system was redesigned to allow optimized management of the fluxes through the system, ensuring precise control and monitoring of oxygen output and CO₂ uptake by the algae. Second, a proper cover for the tank connected to the tubular PBR was designed and installed, making it suitable for microgravity conditions and preventing external contaminations. Third, the lighting system was redesigned: various RGB and white LEDs were strategically positioned, enabling maximized average light intensity and uniform distribution within the PBR (with an 84% decrease in the symmetric percentage difference), thus improving the biomass production rate. The evaluation and selection of microalgal strains was also carried out; in particular, the strain C. vulgaris INETI 58 demonstrated high biomass productivity in both synthetic medium and wastewater, making it a promising candidate for the intended application.