| Astaxanthin has strong anti-oxidation properties,which has outstanding physiological functions,especially in improving immunity,scavenging free radicals and active oxygen.It has wide application value and prospects in food,cosmetics and medicine.Haematococcus pluvialis is currently considered to be an ideal source of biotin.Therefore,research on improving the biomass of Haematococcus pluvialis and the accumulation of astaxanthin in cells is of great significance.Based on the clarified astaxanthin synthesis pathway,this study studied three important substrates in the synthetic pathway: The effects of lycopene,?-carotene and zeaxanthin on the growth of Haematococcus pluvialis and their accumulation of astaxanthin,and the mechanism of their action were analyzed.The results showed that different concentrations of plant pigments had different effects on the growth of Haematococcus pluvialis.When the concentration of lycopene was 0.5 mg/L,the effect was the best.The absorbance at 680 nm was 0.701,and the cell density reached 6.25×105./mL,an increase of 8.51% compared to the control group.The treatment group of l.0 mg/L was followed by an absorbance of 0.672 and a cell density of 6.01×105 cells/mL.When the concentration of ?-carotene was 1.0 mg/L,the best effect was obtained.The absorbance at 680 nm was 0.705,and the cell density reached 6.57×105 cells/mL,which was 9.03% higher than that of the control group.The zeaxanthin-treated Haematococcus pluvialis usually enters the stable phase as early as the 7th day,3 days earlier than the control group.Comparing the cell density on day 10,it was found that 1.0 mg/L zeaxanthin was most beneficial to the growth of Haematococcus pluvialis,with an absorbance of 0.669 and a cell density of 5.98×105 cells/mL,which was improved compared with the control group 3.81%.The effect of adding different plant pigments on the accumulation of astaxanthin showed that when lycopene was added at 0.5 mg/L,the effect of accumulation of astaxanthin on Haematococcus pluvialis was the most obvious,which was 88% higher than that of the control group.The effect of the 1.0 mg/L ?-carotene treatment group was the most obvious.At the 15 th day of treatment,the astaxanthin content of the treatment group was 18.81 mg/L,which was 71.37% higher than that of the control group.The experimental results of zeaxanthin accumulation of astaxanthin in Haematococcus pluvialis showed that its effect on astaxanthin production was not significant.The mechanism of the effect of exogenous pigmentation on the accumulation of astaxanthin was studied.Three key enzymes related to plant pigments in the astaxanthin synthesis pathway were selected,and the levels of key enzyme gene expression in the experimental group and the control group were detected.Under induction conditions,the large-scale synthesis of astaxanthin from Haematococcus pluvialis is often accompanied by high expression of the transcriptional level of astaxanthin synthesis-related genes.The relative expression levels of astaxanthin-related synthetic genes induced by 0.5 mg/L lycopene and 1.0mg/L ?-carotene were determined by qRT-PCR.Under high light and high temperature induction conditions,the astaxanthin synthesis related genes bkt,lcy and CrtR-B in the experimental group showed high expression.The test results showed that the expression levels of ?-carotene ketolase,?-carotene hydroxylase and lycopene ?-cyclase encoding genes under different plant pigment concentrations indicated that bkt,lcy and CrtR-B genes.The amount of expression is directly related to the synthesis of ?-carotene.This indicates that a certain concentration of plant pigment can regulate the accumulation of astaxanthin by changing the expression of key enzyme genes in the metabolic process.The study initially revealed that the addition of plant pigments by exogenous sources can improve the growth of Haematococcus pluvialis and increase the cumulative amount of astaxanthin under stress conditions.It provides new ideas for large-scale farming and astaxanthin production. |
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