Effects of Nitrogen Sources on the Growth and Lipid Content of Phaeodactylum tricornutum

Effects of different nitrogen sources and their concentrations on the growth,total lipids and fatty acids composition of Phaeodactylum tricornutum were studied.The results showed that P.tricornutum growed poorly in cultures without addition of any nitrogen source,but accumulated lipids effectively.The biomass and lipid content of P.tricornutum were promoted simultaneously with more than 3.9 mmol/L of initial ammonium chloride in medium;8.0 mmol/L of urea enhanced the biomass of algae while decreased the lipid content;in the range of tested concentration,sodium nitrate promoted growth of algae and depressed the accumulation of lipid.The fatty acids composition analysis showed that monounsaturated fatty acid(MPUAs) accounted for 45%~50% of the total fatty acids and was less affected by nitrogen sources,thus provided better mobility for biodiesel.The synthesis of C20∶5(n-3)(EPA) and polyunsaturated fatty acid(PUFAs) were increased with addition of nitrogen sources.With 3.9 mmol/L of ammonium chloride,the ratio of EPA and PUFAs to total fatty acids was the highest,20.4% and 26.7%,respectively.