Fig. 1

Cultivation of Chlorella sp. ABC-001 under different CO₂ conditions. a Growth curve of cells cultivated with ambient air and 10% CO₂. The line graph represents cellular density, and the bar graph represents dried cell weight. b The lipid contents of cells as measured after transesterification into FAME. c Changes in nitrate concentration (NO₃⁻) and sulfate concentration (SO₄²⁻). d pH changes. Error bars stand for the standard error calculated from three independent experimental data sets. Asterisks indicate the significant difference between cells cultivated under ambient air and 10% CO₂ determined by Student’s t-test (*P < 0.05, **P < 0.01, ***P < 0.001)