Abstract: The aim of the present study was to investigate the effect of nitrate pulse feeding on the cell growth and cell composition of Desmodesmus sp. F51. Under nitrate pulse-feeding cultivation, the protein content of cells of Desmodesmus sp. F51 decreased from (560 ± 16) mg/g to (456 ± 17) mg/g, while the contents of carbohydrate and lipid increased from (209 ± 13) mg/g to (310 ± 12) mg/g and (98 ± 3) mg/g to (120 ± 4) mg/g, respectively. By investigating the changes in carotenoid, lipid and carbohydrate compositions, it appeared that nitrate pulse feeding could promote β-carotene biosynthesis and enhance the bioconversion of α-carotene to lutein. Lutein accumulation was positively associated with polyunsaturated fatty acid formation. Desmodesmus sp. F51 tended to accumulate carbohydrate as an energy storage product after 3 days of cultivation under nitrate pulse-feeding conditions, and the major accumulated monosaccharide was glucose (75.7 ± 1.4)%. Therefore, the nitrate-pulse feeding strategy is a highly promising approach to simultaneously produce lutein and carbohydrate in Desmodesmus sp. F51.

Key words: microalgae, fed-batch culture, cell composition, lutein, carbohydrate