Docosahexaenoic acid production and ultrastructure of the thraustochytrid Aurantiochytrium mangrovei MP2 under high glucose concentrations

The effect of high glucose concentrations on the ultrastructure and the production of docosahexaenoic acid (DHA) by Aurantiochytrium mangrovei MP2 was investigated at 25°C with orbital shaking. The cultured cells were separated into a floating and a bottom layer after centrifugation during harvest; therefore, the ultrastructure and DHA level were also analyzed separately. Cell size generally increased with glucose concentrations, whereas the overall DHA production (mg/l) increased 19% when the glucose concentration was raised from 6% to 10% w/v. Biomass and DHA production increased significantly, but not linearly, at the floating layer and decreased at the bottom layer in elevated glucose concentrations. Also, the lipid bodies of the cells in the floating layer were more heavily stained in osmium tetroxide than those in the bottom, suggesting that the cells in the floating layer may contain greater amount of unsaturated fatty acids.