Production of eicosapentaenoic acid (EPA) in Monodus subterraneus grown in a helical tubular photobioreactor as affected by cell density and light intensity

The effect of cell density (1-4.5 g L^-1) and light intensity (44 and 82 μmol m^-2 s^-1) on fatty acid composition and eicosapentaenoic acid (EPA, 20:5 ω3) production was studied in a semi-continuous culture of Monodus subterraneus grown in a helical tubular photobioreactor ('Biocoil') under laboratory conditions. Under low light, the highest proportion of EPA (31.5% of total fatty acids) and EPA content (3.5% of dry weight), biomass productivity (1.3 g L^-1 24 h^-1) and EPA productivity (44 mg L^-1 24 h^-1) occurred at optimal cell density of about 1.7 g L^-1. Cell density had no effect on the total fatty acid (TFA) content and was maintained at ca. 11% of dry weight. Under high light, the highest proportion of EPA to fatty acids (31.8%), the total fatty acids content (13.4%) and EPA content (4.3% of dry weight) occurred at cell density of about 3.4g L^-1. But the highest biomass productivity (1.7 g L^-1 24 h^-1) and EPA productivity (56 mg L^-1 24 h^-1) were obtained at a cell density of 1.6 and 2.6g L^-1, respectively. Our results suggest that manipulating the cell density and light intensity can modify the composition of fatty acid and production of eicosapentaenoic acid (EPA) in M. subterraneus.