| Astaxanthin is also called "shrimp flavin", is a red keto-carotenoid. It not only has a powerful oxidation resistance and the ability of free radical scavenging, but also has the function of natural colorants. Astaxanthin is widely applied and has high economic value. And Haemutococcus pluvialis is used as an ideal material to obtain natural astaxanthin, it is recognized as the nature creatures which contain the highest content of natural astaxanthin. Therefore, using Haematococcus phuvialis to scale product astaxanthin has become one of hot topics in the study of international phycology.We studied the effects of different environmental factors on Haematococcus phuvialis growth and the accumulation of astaxanthin and endogenous hormones. In addition, we also made a preliminary study about the dynamic changes of endogenous hormones in the life cycle of Haematococcus pluvialis, and did a preliminary analysis about the relevance between endogenous hormones and Haematococcus pluvialis growth or the accumulation of astaxanthin. In order to make replenishing to the results of previous studies and provide a theoretical foundation for making better use of Haematococcus pluvialis to mass production of astaxanthin.This study showed that the effects of light intensity, temperature and their interaction on Haematococcus pluvialis growth, astaxanthin and endogenous hormone accumulated are significant. When the temperature or light intensity is proper, an appropriate increase in light intensity or temperature can promote cell growth and accumulation of astaxanthin, but high intensity can play an inhibitory effect. Haematococcus pluvialis growth best at 23 ℃ 200μmol·m-2·s-1, the maximum cell density is 4.9 x 105 cells/ml. Experiment resulted that the condition of 27 ℃ 200μmol·m-2·s-1 can conducive to the accumulation of astaxanthin. and the maximum accumulation is 6.266 mg/L. In addition, an appropriate increase in temperature and light intensity can increase the content of ABA of Haemalococcus pluvialis, but if the intensity is too high, it also would inhibit the synthesis of endogenous ABA or accelerated the decomposition of ABA. thereby reducing the accumulation of endogenous ABA. Haematococcus pluvialis at 27℃200μmol·m-2·s-1 conditions, has the highest content of endogenous ABA. and the maximum of ABA is 322.641 n g/g. d w. Besides, for Haematococcus pluvial is. the high temperatures and light intensity can prejudice the accumulation of the endogenous hormone which can promote the growth of the plant. We also find that the Haematococcus pluvialis at 23 ℃ 200μmol·m-2·s-1 conditions has the largest content of GA3, ZR and IAA, the maximum contents are 2.257,73.792 and 35.139 ng/g.dw respectively.This experiment results also show that both carbon source, pH. and their interaction have significant impact on Haematococcus pluvialis growth, the accumulation of astaxanthin and endogenous hormone. Adding exogenous organic carbon can promote cell growth and astaxanthin accumulate of Haematococcus pluvialis. A weak base environment is suitable for cell growth, but an alkaline environment is more conducive to the accumulation of astaxanthin. The condition of G8 (addition of glucose, medium pH is 8) is best for the cells growth, and the maximum cell density is 6.0 ×105/ml. Besides, the conditions of G10 is most favorable to astaxanthin accumulation. The maximum amount is 8.872mg/L. Stress can promote the accumulation of endogenous ABA of Haematococcus pluvialis, and the ABA content in acidic environment is high than it in the alkaline environment; but acidic environment cannot conducive to the accumulation of hormones which can promote the growth of plant. And their content is lower in acidic environment than in alkaline environment. Among them, the content of endogenous ABA at condition of G6 is the highest, and the maximum content is 390.397ng/g.dw. The highest content of endogenous GA3 is in SA8 conditions, and the maximum content is 2.477ng/g.d w. The highest contents of both ZR and IAA are in the G8 conditions, and the maximum are 82.789 and 42.479 ng/g.dw. respectively.Another experiment has researched the dynamic changes of endogenous hormones in life cycles of Haematococcus pluvialis. The results show that the endogenous ABA content is highest in the stage of cyst formation, followed by the stage of cysts maturity, and the lowest content is in the stage of vegetative cells growth; and the content of endogenous GA3, ZR,IAA are both highest in the vegetative cells growth, followed by the stage of cyst formation, and the lowest content are in the stage of cysts maturity. This is mainly related to the different physiological role of endogenous hormones. The highest content of endogenous ABA is always occurs in front of the rapid accumulation of astaxanthin of Haematococcus pluvialis. and the highest contents of both endogenous GA3, ZR and IAA are in the stage of vegetative cells growth, suggesting that there are some correlation not only the accumulation of ABA and astaxanthin, but also the accumulation of endogenous GA3, ZR.IAA and Haematococcus pluvialis cell growth.But the specific roles of endogenous hormones to the growth and astaxanthin accumulation of Haematococcus pluvialis are needed further research to explore the mechanism. |
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