Research On The Fatty Acids And Pigments Of Pleurochrysis Carterae

There are abundant of bioactive substances in microalgae, such as polyunsaturated fattyacids (PUFAs) and pigments, which play various physiological functions and have many healthbenefits to human. It is thus worth developping and utilizing microalgae cells to producePUFAs and pigments. In this research the coccolithophore Pleurochrysis carterae is selected asa model organism, to study the effects of deficiency of nitrogen and phosphorus on the growthand fatty acids of P. carterae under different light intensities and at different temperatures. Wealso studied the efffect of diphenylamine (DPA) on the growth, pigment and fatty acidscompositions of P. carterae. The results obtained for this research can provide basicinformation for further research on fatty acids compositions and on carotenoid biosyntheticpathway of P. carterae, and it will be useful.for producing DHA from coccolithophores forcommercial applications. The major findings are as following:1, under low light (100μmol photons·m-2·s-1) and different temperatures (25°C,15°C),the growth speed of P. carterae decreased variously when P. carterae was cultured in glasscolumn on nitrogen-free and phosphorus-free medium. And the color of the cells was beinglighter. Nitrogen-free resulted in a gradual decline in the culture content of Chl-a with theprolonged incubation time, indicating that nitrogen-free inhibited the synthesis of Chl-a.Moreover, nitrogen-free and phosphorus-free did not induce the massive accumulation of DHAand total fatty acids.When P. carterae was cultured in10L reagent bottle, N-free and P-free cultures haddifferent effects on the growth of P. carterae under low light (100μmol photons·m-2·s-1) anddifferent temperatures (32°C,25°C). At32°C, the growth speed and cell morphology did notchange significantly due to the shorter cultivation time, but the synthesis of DHA and total fattyacids was inhibited by high temperature. At25°C, P. carterae grew slowly on nitrogen-freeand phosphorus-free medium, especially in N-free culture, the cell biomass was small, and thecolour of cultures and cells were pale yellow. Otherwise, the percentage of DHA and TFA (ofdry weight) decreased in N-free and P-free cultures2, under high light (230μmol photons·m-2·s-1) and different temperatures (31°C,28°C,18°C), the growth trend of P. carterae was analogous in nitrogen-free and phosphorus-freecultures. The cell growth rate was very low under N-free conditions, and the culture content ofChl-a decreased constantly. While the growth rate of P. carterae decreased slightly inphosphorus-free culture, the Chl-a content ascensused with prolonged incubation time.Whether in nitrogen-free culture or in phosphorus-free culture, the fatty acid composition ofP. carterae was similar under high light and different temperatures. The percentage of C18:1n9(%of total fatty acids) drastically increased, and the accumulation of the total fatty acids wasinduced in N-free culture, but the synthesis of DHA was inhibited.3, the research initially identified that the primarily yellow pigment in thecoccolithophorid P. carterae was fucoxanthin, and found a pigment absorbing ultraviolet,whose maximum absorption peak was at228nm, presumably it was octahydro lycopene(phytoene).10μM diphenylamine had no apparent effect on the growth of coccolithophoreP. carterae, but it can inhibit the synthesis of fucoxanthin and induced massive accumulation of phytoene, suggesting that absorbing UV light pigment (phytoene) was the synthetic precursorof fucoxanthin. With diphenylamine treatment, the total fatty acids content of P. carteraedecreased slightly, C18:1n9abundantly accumulated, C18:3n3（ALA）、C18:3n6（GLA）andDHA declined variously, indicating that DPA inhibited C18:1further transforming into otherfatty acids.