Variation of lipid class composition in Nitzschia laevis as a response to growth temperature change

The lipid composition and the distribution of fatty acids in the lipid pool were determined in eicosapentaenoic acid (EPA)-producing microalga (Nitzschia laevis) grown under different temperatures. Both the relative amounts of lipid classes and the degree of fatty acid unsaturation in various lipid species were not greatly changed under tested growth conditions. Higher temperature up to 23°C benefited the growth of N. laevis but only had a slight influence on EPA and lipid contents. Further increasing the culture temperature caused a serious inhibition of both the cell growth and fatty acid biosynthesis. Under all temperatures tested, triacylglycerol (TAG) was the predominant lipid constituent (64.5-69.1% of total lipid) and was highly saturated. Lower temperature favored the formation of polar lipids. The highest content of phosphatidylcholine (PC), the major phospholipids component, was reached at 15°C (10.9% of total lipid). In sharp contrast to TAG, PC was highly unsaturated and contained a higher amount of EPA under lower temperature. The highest EPA content in polar lipid was achieved at 19°C. The results from this investigation suggested that the low temperature could improve the distribution of polyunsaturated fatty acids in phospholipids, though it could not significantly influence their amount, especially in PC.