Lipids and ultrastructure of Thraustochytrium sp. ATCC 26185

As a representative of a genus with species considered to be potential commercial producers of the nutritionally important polyunsaturated fatty acid docosahexaenoic acid (DHA), Thraustochytrium sp. ATCC 26185 was investigated to determine its potential for DHA production and lipid composition. Cells from liquid shake cultures contained 32% (w/w) lipid, 18% of which was nonsaponifiable lipid. The major saturated fatty acids (14:0 and 16:0) comprised up to 59% of the total fatty acids, and DHA was up to 25% after 6 d incubation. Squalene represented 63% of the nonsaponifiable lipid, and cholesterol composed 41% of the total sterols. The phospholipids expected for eucaryotic microbes were detected with phosphatidylcholine as the major phospholipid at 76% of the total. The ultrastructure of this species was similar to other Thraustochytrium species except that the cells did not have surface scales and they contained unusual membrane-like structures that appeared to be associated with oil formation.