Seawater desalination concentrate for cultivation of Dunaliella salina with floating photobioreactor to produce β-carotene

Using seawater desalination concentrate to produce microalgae biomass enriched with high value products is a promising way to improve the profitability of desalination industry, but this is seriously limited by enormous land requirement for microalgae farming, as well as high cost of microalgae cultivation. In this study, low cost floating photobioreactor was adopted to cultivate Dunaliella salina to produce β-carotene, using seawater desalination concentrate as culture medium. With carbonate precipitate pretreatment, 97.6% Ca2+ and 60.3% Mg2+ were removed from seawater desalination concentrate. Then, this carbonate enriched medium was bubbled with CO2, to generate bicarbonate, and this increased total inorganic carbon to 0.254 mol L−1. Cultivation with this medium resulted in biomass production without difference from optimized concentrated artificial seawater medium. Pilot scale cultivation of D. salina with floating PBR on ocean showed that 300 g algal biomass containing 14.3 g β-carotene can be produced from 1 m3 desalination concentrate. This amount of β-carotene enriched biomass has a value more than $ 40, and would significantly improve the profitability of desalination industry.