[en] Human interest in long-haul space explorations have been limited due to dearth of basic needs like food, oxygen etc. In this context, the European Space Agency plans to develop an artificial closed system named MELiSSA, capable of harnessing the potential of oxygenic cyanobacteria for production edible biomass and oxygen from waste carbon dioxide and nitrogen in space. This study made the first attempt to evaluate the effect of different concentrations and sources of nitrogen (nitrate, ammonium and urea) on Arthrospira sp. PCC 8005. The cyanobacteria was seen to grow at 2 and 6 mM with maximum biomass yield observed at 12 mM with urea as nitrogen source. The nitrogen assimilation rates were similar at 12 mM for urea and nitrate but were higher for 2 and 6 mM urea. Urea and ammonium were observed to induce changes in the gene and protein expressions, photosynthetic and nitrate-assimilation pathways of cyanobacteria. Effect of high ammonium concentration (28 mM, pH 8.5) on biomass quality and productivity of cyanobacteria was evaluated in continuous-mode photobioreactor wherein changes in composition and profiles of lipids and exopolysaccharide were observed indicating a potential cellular stress.
