Research Of Temperature And Silicon Stress On Growth And Fatty Acids Composition In Phaeodactylum Tricornutum

Polyunsaturated fatty acids(PUFAs) play a key role in human health, especially Eicosapntemacnioc Acid (EPA) and Docosahexaenoic acid (DHA). Human can not synthesize PUFAs (EPA and DHA).When dietary supplement of LA and ALA are added, they can be taken as the substance to produce EPA and DHA, but these amounts can not satisfy the need. So dietary supplement of PUFAs is very important to health. Currently, the principal source of PUFAs is from deep-fish oil.The fish can not synthesize PUFAs, by means of microalgae. However, it is considered insufficient due to an expanding market and a limited resources, this way is far way to satisfy the need.Besides, environment pollution makes more and more heavy metal in the deep-fish oil.It is urgent to exploit safe, continuable and sustainable sources. Marine microalgae have been recently shown to be good alternative sources for their ability to synthesize and accumulate great amounts of PUFAs.In this study, Phaeodactylum tricornutum was chosen for study of their desaturases. The experiment mainly consists of two parts:Firstly, temperature on growth and fatty acids composition in Phaeodactylum tricornutum was studied. Phaeodactylum tricornutum was cultured in batch with different temperatures. Its growth and fatty acids composition were examined.The results showed that the alga grows fast at higher temperatures than at the lower ones, the higher the temperature the faster the growth of the alga. The main fatty acids were C14:0,C16:0,C16:1,c18:1,c18:2,C20:5 (EPA).The percentile content of fatty acids increased first and then decreased to the highest. Microalgal cell which was cultured in 15℃had the higher content EPA(25.71%).Phaeodactylum tricornutum was cultured at 20℃until the end of exponential, then quickly transferred into 4℃, respectively restricted 0,6,12,24h, the result showed that cultured at different temperatures had more fatty acids than stressed different times which only had C14:0,C16:0, C16:1,C18:1,C20:5 (EPA), while the relative contents of EPA up to 30.86%.Furthermore, silicon stress on growth and fatty acids composition in Phaeodactylum tricornutum was also studied. In this experiment,the effects of different Na2SiO3-Si concentrations (0,12,24,48,96 and 384μmol/L)on the cell densities of Phaeodactylum tricornutum were examined. One-way analysis of variance showed that Si produced significant effects on the growth of the Phaeodactylum tricornutum.The cell densities increased with the increase of Si concentration at first,and then decreased with the increase of Si concentrations after reaching the highest values at the concentration of 96μmol/L Si.Phaeodactylum tricornutum is cultured to exponential growth phase in at the concentration of 96μmol/L Si, there are six silicon stress time are set (0,2 h,6h,12h,24h and 48h). The results show that, with the limit time of 6h,48h the EPA content is decreased and increased after 2h,12h,24h si-deficiency, the highest values appeared after 24h si-deficiency.