Mutation Breeding Of Three Kinds Of EPA-rich Marine Microalgae

In order to obtain high-yield EPA marine microalgae, the effect of UV mutagenesis and NTGmutagenesis on the the growth, total lipid and fatty acids of Nannochloropsis oculata,Phaeodactylum tricornutum, Nitzschia closterium were studied. We selected the fine algal strainsand optimized the culture conditions of the mutant strain on its growth,total lipid and EPA.After the UV mutagenesis, the growth rate of the microalgae were changed in varies degree.Seven mutagenesis that grew faster than the wild strain were obtained. Take the growth rate, totallipid content and EPA content into account, Phaeodactylum tricornutum mutagenic strain MP-2was the most successful, its growth rate reached (0.503±0.021), which was1.12times that of thewild strain, total lipid was improved23%, the EPA content also increased.The mutagenic strain MP-2grew best at20℃and its growth rate was inhibited whentemperature exceeded25℃,30℃was its threshold temperature. EPA and PUFA content werehighest at15℃, DHA was highest at10℃.In the20~120μmol/(m2·s) light intensity, MP-20had maximum biomass at40μmol/(m2·s).Low light intensity was conducive to the accumulation of total lipid, at20and40μmol/(m2·s) thatthe MP-2had the highest total lipid content. High light intensity was benefit to the accumulation ofEPA and DHA. At100μmol/(m2·s) light intensity, the cell had the highest level of EPA and DHA.The growth rate of MP-2was highest (0.447±0.013) at salinity25. At salinity30and35, thetotal lipid content of algae was significantly higher than other groups, reached (36.66±1.07)%and(36.54±1.32)%respectively. The MP-2had highest DHA content at salinity25.The growth rate of MP-2was maximum at nitrogen concentration20mg/L. Total lipid contentreached maximum at30mg/L. The PUFA and EPA content reached maximum at25mg/L.The growth rate of MP-2was maximum at phosphorus concentration2.5mg/L.The total lipidcan accumulation more at the low phosphorus concentration1.0mg/L. The EPA and PUFA weresignificantly higher than other groups at best grown phosphorus concentration (2.5mg/L).FeSO4was best iron source. The maximum growth rate was got at5.0mg/L. The best lipidaccumulation was under2.5mg/L iron concentration. The PUFA and EPA content were upwardtrending and reached maximum in concentration10.0mg/L. Under iron deficiency or low ironconditions, the EPA and DHA content is very low or undetectable.The algae can not use the glucose, sodium acetate and glycerol as carbon source forheterotrophic culture.From the point of production, the MP-2cultured at20℃,40μmol/(m2·s) light intensity,25salinity, the20mg/L of KNO3as nitrogen source,2.5mg/L of KH2PO4as phosphorus source, 2.5mg/L of FeSO4as the iron source would obtain high yields of EPA and PUFA.