Study On Physiological And Biochemical Mechanism Of Chromium Enrichment In Cordyceps Militaris

Cordyceps militaris fruit body contains a large number of bioactive components beneficial to human body,with anti-inflammatory,antioxidant,anti-cancer,anti-tumor,improving immunity,lowering blood pressure,lowering blood sugar,lowering blood lipid and other effects.Cr³⁺is the most important component of glucose tolerance factor,which regulates the biological activity of insulin.In this study,the mycelium and fruit body of Cordyceps militaris were cultured by adding different concentrations of Cr³⁺to explore the enrichment characteristics of chromium ions in Cordyceps militaris and the effect of chromium ions on the bioactive components in Cordyceps militaris.1.Comparative screening of chromium ion enrichment ability of Cordyceps militaris strainsIn this study,7 strains from different sources of Cordyceps militaris were collected to compare their Cr³⁺enrichment abilities.Through various strains in Cr³⁺concentration is 0.5 g/L,1.0 g/L two concentrations in liquid medium and oats medium culture,strain 4 of chromium ion content in the mycelia and fruit body significantly higher than the other six strains,and the mycelium and fruit body of FW,DW and increase the contents of PS were significantly higher than other six strains.For strain 4,the content of chromium ion,fresh weight,dry weight and EPS content in Cr³⁺concentration groups 0.5 g/L and 1.0 g/L were significantly higher than those in the control group without Cr³⁺.2.Optimization of chromium ion enrichment conditions in Cordyceps militarisIn this study,strain 4 was used as experimental strain to culture chromium-rich mycelium of Cordyceps militaris by adding different concentrations of Cr³⁺into the culture medium.The results showed that the mycelial growth rate and mycelial biomass of strain 4 were negatively correlated with the increase of Cr³⁺concentration in the medium,and both mycelial growth rate and mycelial biomass reached the maximum value when the Cr³⁺concentration was 0.1 g/L,which was 0.87%and32.78%higher than that of the control group,respectively.The contents of IPS,EPS and chromium ion in Cordyceps militaris mycelia were positively correlated with the concentration of liquid medium Cr³⁺.The contents of IPS and enrichment of Cr³⁺in Cordyceps militaris mycelia reached the maximum at the concentration of Cr³⁺at 1.2g/L,which were 27.70%and 1.34 mg/g higher than those in the control group,respectively.The EPS content of Cordyceps militaris mycelium reached the maximum value at Cr³⁺concentration 1.0 g/L,which was 150.84%higher than that of the control group.The change of antioxidant enzyme activity in Cordyceps militaris mycelia cells under different Concentrations of Cr³⁺was measured.The results showed that the content of MDA in Cordyceps militaris mycelia cells was the highest when the concentration of Cr³⁺was 0.3 g/L,and the mycelia cells were the most stressed by Cr³⁺.When the concentration of Cr³⁺was 0.4 g/L,SOD activity in mycelium cells was the highest,which was 11.18%higher than that in control group.POD activity and CAT activity reached the maximum at 0.6 g/L Cr³⁺concentration,which were 25.21%and 76.28%higher than those in the control group,respectively.The submicroscopic structure of mycelia of Cordyceps militaris was observed by SEM and TEM.The results showed that the surface of chromium-rich mycelia was not smooth and there were particles attached,and there were also metal particles in mycelia.3.Effects of chromium ions on main active components of Cordyceps militaris fruit bodyIn this study,oat medium containing different concentrations of Cr³⁺was used to culture Cordyceps militaris fruit body.The biomass of Cordyceps militaris fruit body and the contents of cordycepin,adenosine,cordycepic acid,ergosterol and chromium ions in the fruit body were determined.In this project,the contents of cordycepin,adenosine and ergosterol in the fruit body were determined by HPLC,and the contents of cordycepic acid and polysaccharide in the fruit body were determined by colorimetric method and phenol-concentrated sulfuric acid method.The results showed that ergosterol increased firstly and then decreased with the increase of Cr³⁺concentration,except that ergosterol decreased with the increase of Cr³⁺concentration.The highest biomass and enrichment of Cr³⁺were obtained at 0.7 g/L of Cr³⁺,which increased 36.85%,35.53%and 202.12%,respectively,compared with the control group.When the concentration of Cr³⁺was 1.5 g/L,the contents of cordycepin and adenosine were the highest,which were 118.75 mg/g and 265.41 mg/g,respectively,increased by 94.61%and 530.29%compared with the control group.The contents of cordyceps polysaccharide and cordyceps acid in fruit body were the highest at the Cr³⁺concentration of 1.1 g/L and 1.2 g/L,which were 1.95 g/kg and 55.17 mg/g,respectively,which were 123.62%and 21.39%higher than those in the control group.The ergosterol content decreased gradually with the increase of Cr³⁺adsorption content in the fruit body.The content of ergosterol in the fruit body was the highest（487.42 mg/g）with the concentration of Cr³⁺at 0.1 g/L,which increased 29.02%compared with the control group.Based on the above studies,the effect of chromium ions on the chemical components in the fruit body of Cordyceps militaris was different,and the order was adenosine>cordyceps polysaccharide>cordycepin>ergosterol>cordycepic acid.In this study,chromium-rich Cordyceps militaris was cultured in solid medium,liquid medium and oat grain medium.The effects of Cr³⁺on biomass,chromium ion content,antioxidant active components and biological active components of Cordyceps militaris were found to be different under different treatments.