| This paper takes Inonotus obliquus as the research object.Through the detection of the yield,properties and biological activity of polysaccharides produced in different fermentation conditions,we explored the effect of fermentation conditions on the production of active polysaccharides by fungi,so as to provide experimental basis for obtaining specific composition and specific activity of Inonotus obliquus polysaccharide components.It also lays the theoretical and experimental foundation for the related research on the metabolism and regulation of medicinal fungi.The main research contents and results of this paper are as follows:(1)The effect of fermentation conditions on the growth status and polysaccharide accumulation of Inonotus obliquusThrough the analysis of experimental results,we found that carbon source,nitrogen source,speed,accelerator,and temperature have certain effects on the mycelium morphology,growth state,and polysaccharide accumulation of Inonotus obliquus.We compared mycelial biomass from high to low,and the results showed that the effect of carbon source on it was corn stover>glucose>sucrose>lactose,and the effect of nitrogen source on it was peptone>soybean meal>ammonium sulfate,and the effect of the speed on it is 180 rpm>150 rpm>120 rpm,and the effect of accelerator on it is Tween-80>oleic acid>control group,and the effect of temperature on it is 28℃>24℃>20℃.Taking the yield of mycelial polysaccharides as the index,we find that the effect of carbon source on it is corn stover>sucrose>glucose>lactose,and the effect of nitrogen source on it is peptone>soybean meal>ammonium sulfate,and the effect of the speed on it is 150 rpm>180 rpm>120 rpm,and the effect of the accelerator on it is oleic acid>control group>Tween-80,and the effect of temperature on it is 28℃>24℃>20℃.We ranked the output of extracellular polysaccharides from high to low,and the results showed that the effect of carbon source on it was corn stover>lactose>sucrose>glucose,and the effect of nitrogen source on it was ammonium sulfate>bean meal powder>peptone,and the effect of the speed on it is 150 rpm>120 rpm>180rpm,and the effect of the accelerator on it is the control group>oleic acid>Tween-80,and the effect of the temperature on it is28℃>24℃>20℃.(2)The effect of fermentation conditions on the physicochemical properties and primary structure of Inonotus obliquus polysaccharideIn different fermentation conditions,There is no significant difference in protein content and polyphenol content of Inonotus obliquus polysaccharide in different fermentation conditions,but the total sugar content and uronic acid content is significant difference,IPSg had the highest total sugar content of 42.39%in the polysaccharides prepared by culture using glucose as carbon source.The polysaccharide of the highest content of uronic acid was IPSsp prepared by culture using soybean cake powder as nitrogen source,and the content of uronic acid was13.65%.In terms of extracellular polysaccharides,the polysaccharide of the highest total sugar content was EPSoa,which was prepared by culture using oleic acid as accelerator,and its total sugar content was 77.75%.The polysaccharides of the highest content of uronic acid were EPScs prepared by culture using corn straw as subsequent carbon source,and the content of uronic acid was 7.86%.Fermentation conditions had little effect on the molecular weight of polysaccharides.The Mw of mycelium polysaccharides prepared in different fermentation conditions were mostly less than 1×10~4Da and their dispersion coefficient was less than 3,while the Mw of IPSl cultured using lactose as carbon source and IPSsp cultured using bean cake powder as nitrogen source were higher than 1×10~4Da,among which the m W and dispersion coefficient of IPSsp were the highest.They are 1.61×10~5Da and 69.74 respectively.The extracellular polysaccharide prepared under different fermentation conditions was smaller in molecular weight,and the highest molecular weight of the extracellular polysaccharide was IPS20 with a m W of about 6000 Da and a dispersion coefficient of 3.98.The monosaccharide composition of polysaccharides was affected by fermentation conditions.Mycelium polysaccharides are mainly composed of glucose,mannose and galactose,with a small amount of xylose and glucuronic acid.Different fermentation conditions had different effects on the monosaccharide composition of mycelium polysaccharides.Taking carbon source as an example,we found that the mycelium polysaccharide IPScs prepared using corn straw as the subsequent carbon source also contained rhamnoose and galacturonic acid,and the mycelium polysaccharide IPSg prepared using glucose as the carbon source also contained fucose.In terms of extracellular polysaccharides,the main monosaccharide component was glucose,and its content was all above 55%.However,in different fermentation conditions,the monosaccharide types and proportions showed certain differences.Neutral and acidic sugar fractions were obtained by DEAE Sepharose anion exchange chromatography.In terms of mycelium polysaccharides,the polysaccharides prepared under different fermentation conditions all contained neutral sugar component and one acidic sugar component,but the content ratio was different.In terms of extracellular polysaccharides,the main component of polysaccharides prepared under different conditions is neutral sugar,while the polysaccharides EPS180,EPSoa and EPSt80 contain acidic sugar..(3)The effect of fermentation conditions on the antioxidant activity and hypoglycemic activity of Inonotus obliquus polysaccharidesThe polysaccharides from mycelia and extracellular polysaccharides in different fermentation conditions had certain DPPH radical scavenging activity,hydroxyl radical scavenging activity,ferrous ion chelating activity and reducing power,and there was dose effect at the same time,but the activities of different polysaccharides were different.The extracellular polysaccharides(except EPSas)prepared in different fermentation conditions had inhibitory effects onα-glucosidase,the inhibitory effect of EPScs and EPSlα-glucosidase is lower than the positive control acarbose,the inhibitory effects of other extracellular polysaccharides are higher than the positive control,the activity of EPSs highest.Different fermentation conditions had different effects onα-glucosidase inhibitory activity of extracellular polysaccharides.Using the insulin resistance model of Hep G2 cells,we compared the improvement of insulin resistance by polysaccharides of Inonotus obliquus prepared in different fermentation conditions.The results showed that both mycelium polysaccharides and extracellular polysaccharides could improve the insulin resistance of cells,but there were differences in the effect of fermentation conditions on the activity of polysaccharides.Among them,nitrogen source conditions had the greatest effect on the improvement of cell insulin resistance.IPSp and EPSsp prepared taking peptone as the nitrogen source had the strongest effect on the improvement of cell insulin resistance. |
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