Cryopreservation And Mutagenesis Breeding Of High Yield EPA Marine Microalgae

Marine microalgae could generate PUFAs such as EPA and DHA,which possess high value in medical and health care products. Chlorellaand Phaeodactylum tricornutum are single-cell microalgae and mostfrequently used in aquaculture because they have high value of nutritionand contain abound unsaturated fatty acids. In order to obtain algal strainsof high EPA production, it is necessary to research the aglae’s vitrifiedpreservation, culture conditions and mutation breeding。Cryopreservation of the microalgae is suggested by other studies asthe best method for long-term storage. Cryoprotectant agents such asglycerin, DMSO, ethanediol, propanediol, trehalose and sucrose wereused to test the efficacy of the microalgae cryopreservation. The resultsindicated that the highest survival rates of Chlorella vulgaris andPhaeodactylum triconutum could reach70.2%and45.6%usingcryoprotectants consists of ethanediol, glycerin and sucrose.The conditions of culture and EPA production of the two microalgaewere studied. The results showed that the most suitable foster conditionfor EPA accumulation of chlorella were as follows:150mg/L NaNO3,10mg/L Na2HPO4·2H2O,5mg/L Na2SiO3·9H2O,1.09mg/L Na2·EDTA,and0.5mg/mL6-BA. Under the condition, the growth rate is0.2606andthe EPA content is21.26mg/g, which increased by86.3%and53.7%respectively compared with using the F/2medium. The most suitablefoster condition of Phaeodactylum tricornutum includes:75mg/L NaNO3,2.5mg/L Na2HPO4·2H2O,10mg/L Na2SiO3·9H2O,2.18mg/L Na2·EDTA,0.5mg/L6-BA,10mg/L IAA. Under the suitable foster condition, thespecific growth rate and EPA content were increased by70.8%and66.6%respectively.The effects of UV and EMS mutagenesis to the ocean microalgaecells were studied. The results demonstrated that the appropriate radiationdoses of chlorella and Phaeodactylum tricornutum were20min and15min under ultraviolet irradiation range35cm; and the suitableconcentration of EMS were0.8%and0.6%respectively. Four strains of mutants were isolated by single cell clone and named UC1, EC1, UP1and EP1. Their EPA contents were increased by2.28%,8.97%,19.50%and24.88%respectively. The suitable foster conditions for EPAproduction of the mutation strains were studied. The results showed thatthe best condition for UC1, EC1, UP1and EP1were as follows:75mg/LNaNO3, pH7.5, day-night temperature23-21℃,17-15℃,17-15℃and17-15℃respectively, inoculation quantity was7%,12%,10%and12%respectively,13,7,7and7training days respectively. The mutationstrains possess good genetic stability.