Response of growth and fatty acid compositions of Nannochloropsis sp. to environmental factors under elevated CO2 concentration.

Nannochloropsis sp. was grown with different levels of nitrate, phosphate, salinity and temperature with CO(2) at 2,800 microl l(-1). Increased levels of NaNO(3) and KH(2)PO(4) raised protein and polyunsaturated fatty acids (PUFAs) contents but decreased carbohydrate, total lipid and total fatty acids (TFA) contents. Nannochloropsis sp. grew well at salinities from 22 to 49 g l(-1), and lowering salinity enhanced TFA and PUFAs contents. TFA contents increased with the increasing temperature but PUFAs contents decreased. The highest eicosapentaenoic acid (EPA, 20:5 omega3) content based on the dry mass was above 3% under low N (150 microM NaNO(3)) or high N (3000 microM NaNO(3)) condition. Excessive nitrate, low salinity and temperature are thus favorable factors for improving EPA yields in Nannochloropsis sp.