Incorporation of Exogenous Docosahexaenoic Acid into Triacylglycerols and Polar Lipids of <i>Chlorella vulgaris</i>

Abstract

Docosahexaenoic acid (DHA)-enriched Chlorella vulgaris is commonly used as a feed in fisheries and as a dietary supplement. The time course DHA uptake into the Chlorella cells and incorporation of DHA into the triacylglycerols (TAG) and polar lipids (PL) were examined. After the addition of DHA into the Chlorella culture, DHA was rapidly taken up by the Chlorella cells and was mainly incorporated into TAG. However, some DHA was also incorporated into PL molecules. Although the percentage of DHA in the total fatty acids of total cellular lipids reached at 67%, the percentage in the total fatty acids of PL was 27.5%. As for the effects of pH, exogenous DHA was mainly incorporated into TAG molecules at pH 5-7. At pH 3-4 and 8, the DHA accumulated as free fatty acid in the cells. The exogenous DHA was rapidly incorporated into TAG molecules within 24 hours at pH 5-8. The findings should contribute profitably to production of better fishery feed and food supplement by using DHA-enriched Chlorella.