Screening for alkaliphilic microalgae for carbon capture from ambient air and food production

The production of alkaliphilic microalgae can contribute to address the challenging cost of using pure carbon dioxide in large reactors. At high pH values, carbon dioxide is rapidly scavenged and the supply rates of dissolved inorganic carbon from the atmosphere to alkaline media are high. The present study aimed to identify microalgal strains that can cope with high alkalinity and aeration rates. Eight strains were studied and the microalgae Chlorella vulgaris, Scenedesmus almeriensis and Nannochloropsis gaditana were the only ones that were able to grow under these conditions. Their biomass productivities using laboratory-scale bubble columns with no pH control and high aeration flow were 0.20 +/- 0.03, 0.24 +/- 0.03 and 0.08 +/- 0.01 g<middle dot>L-1<middle dot>day(-1), respectively. The production of the two former was scaled up to pilot-scale bubble columns. Overall, the amount of atmospheric carbon dioxide that was transformed into biomass was in the range of 10%-30%, depending on the strain used and the photobioreactor setup. The biomass was rich in proteins and beta-carotene, both valuable products, highlighting the potential production of food ingredients while capturing carbon dioxide from the atmosphere.