Optimization Of Haematococcus Pluvialis LUGU Culture Conditions And Investigation On Its Mechanisim Of Astaxanthin Production With Fluic Acid Induction

Haematococcus pluvialis could accumulates large amounts of secondary metabolite-astaxanthin under extreme environmental stress conditions.A novel strain of high-astaxanthin production by Haematococcus pluvialis LUGU,which was isolated from Lugu Lake in Yunnan Plateau,and using Haematococcus pluvialis LUGU as the experimental subject in this study.During growth stage,high-density cultivation of Haematococcus pluvialis by optimizing the experimental conditions was utilized,the effects of four factor on the biomass productivity of Haematococcus pluvialis LUGU was investigated,to screen the factors of conducive to the growth of microalgae to optimize the experimental design in order to effectively increase the biomass productivity.Under induction period,the influences of fulvic acid?FA?on biomass and astaxanthin accumulation were investigated,and transcriptional levels of three astaxanthin biosynthetic genes in H.pluvialis,namely,phytoene desaturase?PDS?,lycopene cyclase?LCY?,and ?-carotene hydroxylase?CHY?,were measured.Molecular mechanism of astaxanthin production with FA induction was explored,and demonstrated a useful strategy to efficiently produce astaxanthin by using H.pluvialis.The concrete results are summarized as follows:?1?A novel strain named Haematococcus pluvialis LUGU was identificated from Lugu lake in Yunnan Plateau based on its morphological and 18S rRNA molecular phylogenetic tree,the photo bioreactors were utilized high-density cultivation of Haematococcus pluvialis cells to achieve a high cell density of 1.2×106 mL^-1.In addition,it was found that Haematococcus pluvialis LUGU had a good capacity to accumulate astaxanthin,the total astaxanthin content reached 20.14 mg g-1 which was higher than other microalgal species,and higher than the genes Haematococcus,pluvialis.Therefore,Haematococcus pluvialis LUGU has a large market competitiveness.?2?According to the results of the single factor orthogonal experiments,sodium nitrate,fulvic acid and salicylic acid were significantly affect the growth of Haematococcus pluvialis LUGU.The results of three factors and three levels orthogonal experiments showed that sodium nitrate was the extremely significant factors?p<0.01?on the growth of H.pluvialis LUGU and the factor of fulvic acid was the significant factors?p<0.05?,salicylic acid was the undistinguished factor?p>0.05?.?3?The biomass content of H.pluvialis were increased 4.13%and 5.44%than controls,astaxanthin content increased by 86.89%and 9.78%in 5 and 10 mg L^-1 FA-treated algal cells,respectively.The transcriptional levels of PDS,LCY,and CHY genes were also improved under FA induction,and FA treatments had a great effect on the transcriptional expression levels of PDS and CHY than on LCY.Those results showed that transcriptional upregulation of PDS and CHY provide rate-limiting steps for astaxanthin biosynthesis in Haematococcus pluvialis LUGU with FA induction.