| Abstract |
As space missions extend in duration and distance, there is an increasing need for autonomous life-support systems capable of recycling resources and producing essential compounds in situ. In this context, alginate-entrapped microalgae were used to assess growth under reduced liquid conditions, testing two different beads-to-volume ratios (1:1 and 1:2). In batch cultures conducted in flasks without aeration, the immobilized microalgae using HEPES-Acetate-Phosphate (HAP) medium reached a maximum dry weight (DW) of 0.93 ± 0.03 g/L and 33.65 ± 1.19 x 106 cells/mL in the 1:2 configuration, compared to 1.01 ± 0.02 g/L and 37.44 ± 1.56 x 106 cells/mL in suspension. Biomass productivity peaked at 404 mg/(L·d) for suspension and 240 mg/(L·d) for 1:2 immobilized cultures. Biochemical analysis of immobilized biomass revealed high nutritional value, with up to 32.5 % DW lipids, 23.6 % DW proteins, and 12.5 % DW carbohydrates. In the pre-prototype column reactor with medium recirculation and air bubbling, microalgae showed lower productivity than in batch tests indicating the need for further optimization of process configuration. Immobilized Chlorella vulgaris offers a trade-off between reduced productivity and engineering advantages, such as ease of recovery, and suitability for automated, closed-loop bioregenerative in space life-support systems as well as for terrestrial application.
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