Enhancing carbon dioxide fixation and co-production of protein and lutein in oleaginous Coccomyxa subellipsoidea by a stepwise light intensity and nutrients feeding strategy.

To achieve high-efficient CO fixation and co-production of protein and lutein, a stepwise light intensity and nutrients feeding strategy in two-phase cultivation was developed after optimization in one-phase culture of oleaginous C. subellipsoidea in this work. Results showed the incremental light intensity and CO feeding boosted biomass production in phase 1, then a decreased light intensity and CO feeding with nitrate addition enhanced protein and lutein synthesis in phase2. The highest biomass (9.40 g/L) and average CO fixation rate (1.4 g/L/d) were achieved with excellent content and productivity of protein (52.36% DW, 435.72 mg/L/d) and lutein (1.65 mg/g, 1.37 mg/L/d) with 40.27% of light-energy saved. While the highest contents of total amino acids (42.38% DW) and essential amino acids (17.65% DW) were obtained with an essential amino acid index (1.2) compared with FAO/WHO reference. This study provided a promising application scenario of oleaginous microalgae for carbon neutrality and multiple high-value compounds co-production.