High lipid content and productivity of microalgae cultivating under elevated carbon dioxide

This study examined the cell growth rate, lipid contents, lipid productivity, chlorophyll a concentration, and carbon dioxide tolerance of Chlorella vulgaris

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under various cultivation conditions. The pH, concentration of carbon dioxide in media, and light intensity variables were manipulated to obtain high lipid productivity. The optimum conditions were at pH 7.0, 2,930 lux, and 30 % carbon dioxide. Biomass concentration reached 1,288, 1,130, and 1,083 mg L^-1 at 15, 30, and 50 % CO₂ after 6 days, respectively, implying that this strain has appreciable tolerance to carbon dioxide. The highest concentration of chlorophyll a occurred at 2,930 lux and decreased with increasing light intensity gradually. The maximum specific growth rate was 3.25 day^-1 based on the dry weight and 4.63 day^-1 based on the cell number. The lipid content (45.68 %) and lipid productivity (86.03 mg day^-1 L^-1) obtained in this study are higher than reported values in literatures. Hence, C. vulgaris is a good candidate for subsequent research in biodiesel production under elevated carbon dioxide concentration by microalgae.