Study On The Mechanism Of Exogenous Compounds Regulating Growth Rate And Epa Synthesis Of Phaeodactylum Tricornutum

Phaeodactylum tricornutum is a marine diatom, which has drawn wide attention in recent decades because of its abundant EPA. EPA (eicosapentaenoic acid,20:5△5,8,11,14,17) benefits human health, especially for cardiovascular, inflammation and cancer prevention and treatment. Like some other active substances, the industrilization of EPA from Phaeodactylum tricornutum, has been faced with the problems of low yields, higher costs and other issues. There has been studies illustrating that higher light intensity could increase the EPA proportion of Phaeodactylum tricornutum. However, this kind of increase tended to be accompanied by the decrease of biomass, whose mixed results led to the restriction of Phaeodactylum tricornutum. This research tries to resolve this embarassment.Chitosan has attracted more and more attention due to its physiological and biochemical activities in recent years. It could play roles in increasing the proportion of seed germination, antibacteria, stress tolerance, parasiticide, soil improvement and many other functions. NO is a signal molecule attracted much attention and its research in plants and algae is still at an early stage. NO plays an important role in plant stress resistance to external factors. In addition, it plays a positive role in plants’germination, growth and reproduction. All the above gives us a hint that either of them could be the insurance of the biomass of Phaeodactylum tricornutum.This study found that low concentration of chitosan inhibits the growth of Phaeodactylum tricornutum, which may be due to the difficulty to be dissolved in the seawater. Maintaining the amount of NO, when Phaeodactylum tricornutum was cultured under1000,4000,6000lux light intensity, EPA content increased with the light intensity increased, which was more significant in the experiment groups(experiment groups with the addition of NO, control groups without).The growth Phaeodactylum tricornutum has been promoted in the50nM SNP f/2medium. Under1000,4000,6000lux light intensity, compared to the control groups, the cell density of the experiment groups were increased by4%,5%and4%. Relative to the control group, the experiment groups had biomass increase, respectively, by14%,12%,18%. As the light intensity increases, both chlorophyll a and carotene had a significant increase, chlorophyll b was decreased. Under1000,4000,6000lux conditions, the chlorophyll a of experiment groups increased by, respectively,5%,15%, and6%, and chlorophyll b were reduced by19%,6%, and46%, and carotene, respectively, increased by11%,21%and8%than the control groups. Under1000,4000,6000lux conditions, relative to the control group, the MDA content of the experiment group decreased by3%,30%, and22%, and SOD activity increased by28%,50%, and44%, and ascorbate peroxidase activity increased by25%,23%,21%compared to the the control groups under the same light intensity. Under1000,4000lux light intensity, glycolic acid oxidase activity in the experiment group were lower than the control groups, and under6000lux light intensity the experimental group was higher. The former may be associated with increased cell dry weight, the latter may be associated with resistance to access light. NO improves the EPA content of Phaeodactylum tricornutum, which may be related to the enhanced antioxidant enzyme activities, the regulation of the glycolate oxidase activity which affects photosynthesis, increase of its cell dry weight, and the affected fatty acid ratio.