Carotenoid production from Chlorococcum littorale in photoautotrophic cultures with downstream supercritical fluid processing

Carotenoid production from highly CO₂ tolerant microalga Chlorococcum littorale in photoautotrophic cultures with downstream supercritical fluid processing was studied. Increasing temperature, increasing light intensity and decreasing CO₂ and O₂ gas concentrations enhanced growth rate under nitrate-rich conditions. Carotenoid content was insensitive to nitrate concentration, temperature and gas composition, but was greatly promoted by light intensity. Growth rate and carotenoid content had an optimum light intensity of ca. 120 μmol-photon·m⁻²s⁻¹. Separation of two sample cultures was studied by applying supercritical fluid extraction with CO₂ and 10 mol% ethanol co-solvent. Extraction yield of carotenoids was 90% with 10 mol% ethanol at 333 K and 30 MPa. Selectivity of a sample with less lipid content (12.9 wt%) was five-fold higher than that with higher lipid content (29.4 w%).