Optimization of production of docosahexaenoic acid (DHA) by Thraustochytrium aureum ATCC 34304

Abstract

By varying culture carbon source, lipid content in mycelium of Thraustochytrium aureum ATCC 34304 varied widely in the range 1–25% of biomass weight. Docosahexaenoic acid (DHA) content of mycelium lipid was higher (65–76%) when biomass lipid content was very low (1–2%) and lower (40–50%) when biomass contained a high lipid content (14–18%). DHA yields from glucose, starch and maltose were 270, 325 and 334 mg/L, respectively. DHA yield and content of biomass was optimal at an initial culture pH of 6.0. During the culture cycle of T. aureum, DHA content in lipids remained relatively constant with optimal DHA yield being observed after six days. Biomass, lipid content in biomass, DHA content in biomass and DHA yield were all optimal at a cultivation temperature of 28°C. However, the proportion of DHA in lipids declined with increase in temperature. Biomass, lipids in biomass and DHA yields were 13%, 42% and 47% higher, respectively, din light‐exposed cultures as compared to dark cultures. A maximum yield of DHA of 511 mg/L was observed in light‐ exposed cultures containing 2.5% starch, where lipids accounted for over 20% of biomass dry weight.