Effects of nitrogen source and vitamin B12 on docosahexaenoic acid production by Crypthecodinium cohnii

Abstract

The effects of nitrogen sources and vitamin B12 on cell growth and docosahexaenoic acid (DHA, C22:6 ω-3) content of Crypthecodinium cohnii ATCC 30556 were investigated. Among the three nitrogen sources (tryptone, yeast extract and corn steep liquor) used, tryptone was the best nitrogen source for C. cohnii. The highest specific growth rate (0.087 h-1) and DHA content (64.34% of total fatty acids) were achieved at a tryptone concentration of 1 g/l. Vitamin B12 was not an essential nutrient for the growth of C. cohnii. However, an addition of vitamin B12 to the medium exhibited stimulating effect on the growth of the alga as reflected by a higher specific growth rate and a higher biomass concentration. The highest biomass concentration (2.48 g/l) was obtained at a vitamin B12 concentration of 0.75 µg/l. The results suggest that nitrogen source should be properly selected and vitamin B12 should be added in the defined artificial medium for the optimal production of DHA by C. cohnii.