Effects of organic carbon sources on cell growth and eicosapentaenoic acid content of Nannochloropsis sp.

A strain of Nannochloropsis isolated originally from the East China Sea and obtained from Institute of Hydrobiology, Chinese Academy of Sciences was shown to utilize glucose or ethanol for mixotrophic and heterotrophic growth. The highest cell density, 550 mg L-1 dry weight after culture for 8 days, was obtained during mixotrophic culture with 30 mM glucose. The organic carbon sources had no effect on the net photosynthetic rate, but enhanced the respiratory rate. The addition of an organic carbon source led to an increase in the cell lipid content and a decrease in their eicosapentaenoic acid (EPA) content. The EPA yield was 21.9 mg L-1 using photoautotrophic culture, and 23.4 mg L-1 and 23.0 mg L-1, respectively, in mixotrophic cultivation with glucose or ethanol as the carbon source.