STUDIES ON THE PRODUCTION OF OIL AND POLYUNSATURATED FATTY ACIDS IN FIVE SPECIES OF NANNOCHLOROPSIS

Nannochloropsis species are known for high contents of oil or polyunsaturated fatty acids (PUFA), such as EPA (C20:5). In Nannochloropsis species, oils contain essentially saturated and mono-unsaturated fatty acids, while polar lipids are rich in PUFA. In this study, total lipids, oils and fatty acids were analyzed in 5 Nannochloropsis species. Total lipids were extracted from cells using chloroform/methanol, and from total lipids, triacylglycerols were purified using thin layer chromatography. Of the five species, four were found to be of high-oil contents and one of very low-oil content. In the high-oil species, lipids could be accumulated to more than 57% of cell dry weight at late stationary growth phase, of which triacylglycerols accounted for 32.4%–45.2% of cell dry weight. The fatty acid composition of whole cells of all five species or triacylglycerol of four high-oil content species was analyzed. In high-oil content species, saturated and mono-unsaturated fatty acids accounted for more than 95% of total fatty acids, while the polyunsaturated fatty acids were less than 5%. In contrast, in the species of low-oil content, polyunsaturated fatty acids accounted for more than 45% of total fatty acids. Triacylglycerols of the four high-oil content species possessed less than 4% PUFA and may serve as excellent raw materials for biodiesel production. On the other hand, EPA may be easily produced from total lipids of the low-oil content Nannochloropsis.