Docosahexaenoic Acid Yield Research Articles

Effect of benzyl viologen on the phospholipid fatty acid composition and some properties in hepatic microsomal membrane of rats

The effect of benzyl viologen (a stimulator of free radical production in cells) on lipid composition, fluidity and enzymes involved in both polyunsaturated fatty acid biosynthesis and cholesterol metabolism was studied in liver microsomal membrane of adult rats. In viologen-treated animals, a significant decrease in the levels of free cholesterol and cholesteryl esters, accompanied to a decrease at the free cholesterol/phospholipid ratio, were observed. The levels of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and acyl-coenzyme A: cholesterol acyltransferase (ACAT) were also lower in viologen-treated rats than in controls. Linoleic and arachidonic acids were both severely lower while docosatetraenoic, docosapentaenoic and docosahexaenoic acids were significantly higher as compared with controls. Furthermore, a decrease in monounsaturated/saturated ratio was found. In addition, the treatment evoked a depression in the fatty acid desaturation complex, with a diminish of delta 9, delta 6 and delta 5 desaturase activities in microsomal membrane. It was concluded that changes in phospholipid microsomal fatty acid and cholesterol content could be directly responsible for changes in membrane fluidity and function, and that extensive yield of docosahexaenoic acid may serve to maintain the physical characteristics of particular domains against oxidative stress caused by benzyl viologen treatment.

Production of docosahexaenoic acid by Thraustochytrium aureum

Thraustochytrium aureum ATCC 34 304 contained approximately 50% of total fatty acids as docosahexaenoic acid (DHA). Lipid content of the biomass was dramatically influenced by medium composition and ranged from 0.3 to 16% of the biomass weight. Increasing the culture medium glucose concentration from 5 to 20 g/l caused the lipid content of the biomass to increase from 2.7 to 16.5% and the DHA yield to increase from 26 to 270 mg/l of whole culture broth. The proportion of DHA in lipids was independent of glucose concentration. The fatty acid profile observed in the high-yielding DHA culture was: 16:0, 19.2%; 18:1, 9.8%; 18:2, 2.4%; 20:4, 4.9%; 20:5, 3.6%; 22:6, 48.5% and others, 7.1%. For DHA production, fungal cultures were incubated on an orbital shaker under light at 25° C for 6 days.

Optimization of production of docosahexaenoic acid (DHA) byThraustochytrium aureum ATCC 34304

AbstractBy varying culture carbon source, lipid content in mycelium ofThraustochytrium 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 ofT. 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.