Regulation Of Culture Conditions On Accumulation Of Astaxanthin In Haematococcus Pluvialis

Astaxanthin produced by Haematococcus pluvialis is widely used in food,health care products and aquaculture because of its strong antioxidant activity and enhanced immunity.In this study,Haematococcus pluvialis was used to optimize the stress treatment conditions(light intensity,NaCl concentration,NaNO₃concentration)by experimental ecological methods,and the photochemical behavior and metabolites of Haematococcus pluvialis were analyzed.To achieve the purpose of high-yield astaxanthin.The results are as follows:1.Using chlorophyll fluorescence technique to study the effects of light intensity,NaCl concentration and NaNO₃concentration on photosynthesis of Haematococcus pluvialis.The results showed that:(1)On day 26,the Fv/Fm values of the control group,73,127,182,236,and 291?mol/m²·s^-1on the first day of the experiment decreased by 8%,37.9%,29%,37.9%,and32.4%,respectively.And 27.7%.(2)When the NaCl concentration was 10 and 12.5 g/L,the Haematococcus pluvialis Fv/Fm and Yield values were lower than the control group,while the microalgae Fv/Fm and the Yield value were higher than the control group at 5 g/L.(3)When the concentration of NaNO₃was 0,0.032 and 0.065 g/L,the whole Fv/Fm of Haematococcus pluvialis increased first and then decreased slowly,which was significantly different from the control group(P<0.05).2.Effects of light intensity,NaCl concentration and NaNO₃concentration on accumulation of astaxanthin in Haematococcus pluvialis(1)There were significant differences between the treatment groups of different light intensity and the control group(P<0.05).On the 24th day of the experiment,the content of astaxanthin accumulated in Haematococcus pluvialis reached the highest,and the highest content of astaxanthin(9.01 mg/L)was accumulated when the light intensity was 236?mol/m²·s^-1.(2)There was no significant difference compared with the control group when the salt concentration was 0 and 12.5 g/L(P>0.05).On the 24th day of the experiment,when the salt concentration was 7.5 g/L,the accumulated astaxanthin content reached the highest,which was 34.4%higher than that of the control group.(3)Under the condition of nitrogen stress treatment,the content of astaxanthin accumulated by Haematococcus pluvialis gradually increased,and the astaxanthin accumulated by microalgae gradually stabilized after the 22nd day of experiment.When the nitrogen concentration was 0 g/L,it was significantly higher than the other treatment groups(P<0.05),and there was no significant difference between the treatment groups(P>0.05).(4)Using the response surface methodology(RSM)to study the interaction of light intensity,NaCl concentration and NaNO₃concentration to optimize the synthesis of astaxanthin ester in Haematococcus pluvialis.The optimal combination of response function was light intensity182?mol/m²·s^-1,NaCl concentration 7.5 g/L and NaNO₃concentration 0.13 g/L,the astaxanthin yield was up to 19.24 mg/L.3.This experiment explored three stress treatment groups of Haematococcus pluvialis by means of metabolomics research(light intensity 236?mol/m²·s^-1,NaCl concentration 7.5 g/L and nitrogen concentration 0 g/L).Differences in metabolites and metabolic pathways from the control group.The results show:(1)The light treatment group detected 31 metabolites by LC-MS,mainly nitrogen-containing small molecules and carbon metabolites.Heat map analysis showed that compared with the control group,the content of energy center compounds and nucleic acid metabolites in the microalgae of the light treatment group decreased significantly(P<0.05),and the level of amino acid metabolites was up-regulated.(2)A total of 46 metabolites were detected in the salinity stress treatment group,including 14 amino acids and their derivatives,5 organic acids related to energy metabolism,and 16 nucleotides and derivatives.Heat map analysis showed that the content of base metabolites and nucleic acid metabolites in the microalgae of the salinity treatment group was significantly lower than that of the control group(P<0.05).(3)A total of 73 metabolites were detected in the nitrogen-stressed treatment group.The heat map showed that nitrogen stress significantly decreased the expression of amino acid metabolites and carbohydrate metabolites in the microalgae cells compared with the control group(P<0.05).