Effects of light intensity,nitrogen sources,and nitrogen levels on the growth,total lipids,and arachidonic acid accumulation of Parietochloris incisa

Parietochloris incisa(Reisigl) S.Watanabe is one of the most promising microorganisms in future health care due to its high arachidonic acid (AA) content.In this study,growth rate and total lipid and AA accumulation in P.incisa were studied under two different light intensities,three different nitrogen sources,and five different nitrogen concentrations.Results showed that three nitrogen sources were utilized by P.incisa.With the increase in light intensity,the growth rate of P.incisa and the contents of total lipids and AA increased significantly under higher nitrogen concentrations.The highest biomass (4.17 g·L^-1) was obtained under 300 μmol·m^-2·s^-1 with 8.8 mmol·L^-1 NaNO₃ after 14 d of cultivation.For NaNO₃,NH₄HCO₃,and CO (NH₂)₂ nitrogen sources,the highest total lipid contents were 41.17%(1.0 mmol·L^-1),42.04%(1.0 mmol·L^-1),and 39.96%(0.5 mmol·L^-1),respectively,under the 100 μmol·m^-2·s^-1 condition.Moreover,the maximum AA content (16.44% DW) of P.incisa was achieved under 300 μmol·m^-2·s^-1 with 2.9 mmol·L^-1 NaNO₃.The highest lipid and AA productivities were 134.60 mg·L^-1·d^-1(1.0 mmol·L^-1) and 35.85 mg·L^-1·d^-1(2.9 mmol·L^-1) respectively,under 300 μmol·m^-2·s^-1 light intensity and NaNO₃ nitrogen source condition.Considering the cost factors,NH₄HCO₃(5.9 mmol·L^-1) and CO (NH₂)₂(2.9 mmol·L^-1) as nitrogen sources under 300 μmol·m^-2·s^-1 high light intensity is recommended for P.incisa cultivation for AA production.