Regulation Of Liquid Fermentation And Immunostimulant Activity Studies On Extracellular Polysaccharides From Ganoderma Lucidum

As a traditional Chinese herbal medicine,Ganoderma lucidum(G.lucidum)can benefit the heart,calm the soul,strengthen the bones,and has a high medicinal value.The recent research shows that G.lucidum polysaccharide has many biological activities such as anti-tumor and immunity enhancement.The production of G.lucidum polysaccharide by liquid fermentation has the advantages of high yield and short cycle,and has been widely concerned by researchers at home and abroad.However,the research on the production of G.lucidum polysaccharides by fermentation method mainly focuses on the optimization of fermentation conditions and the screening of strains.There are few studies on the structural characteristics of polysaccharides derived from fermentation,especially extracellular polysaccharides.In this paper,based on the screening of high-yield strains of extracellular polysaccharides,the effects of carbon and nitrogen sources on the structural characteristics of extracellular polysaccharides were explored.The structure-activity relationship was investigated through activity comparison,which laid a foundation for the development and utilization of G.lucidum fermentation extracellular polysaccharides.In this study,ten strains of G.lucidum were cultured by liquid fermentation to compare the mycelial biomass,the yields and content of extracellular polysaccharides,and monosaccharide composition characteristics.Extracellular crude polysaccharide yields of two strains,G0023 and G0160 reached 3.02 and 3.14g/L in 7 days,and polysaccharide content was 84.11% and 91.03%,respectively.And they could be regarded as excellent strains for producing extracellular polysaccharides.Analysis of ethanol fractional precipitated extracellular polysaccharides showed that the fermentation broth mainly contained high molecular weight polysaccharide fractions.The composition analysis of monosaccharides showed that they were composed principally of glucose and contained a small amount of xylose and mannose.The apparent viscosity of extracellular fluid was positively correlated with the yield and polysaccharide content of the macromolecular polysaccharide component of the strain.The results of activity comparison showed that the 20 E components(precipitated with20% ethanol)of the extracellular polysaccharides of each strain had the activity of enhancing immunity,and the 20 E polysaccharide fractions obtained from fermentation broths of G0023 and G0160 exhibited the highest activity.The fermentation of G0160 strain was carried out in different carbon and nitrogen source combined medium to explore the effects of carbon and nitrogen sources on the content and structure of extracellular polysaccharides.The results showed that the change of carbon source and nitrogen source will affect the yields and monosaccharide compositions of polysaccharide fractions obtained by ethanol precipitation.Obviously,the yield and polysaccharide content of the polysaccharide fractions(20E)precipitated with 20% ethanol were both high.The results of monosaccharide composition analysis showed that the carbon and nitrogen sources had obvious effects on the kinds and ratios of monosaccharides in the extracellular polysaccharide fractions.When yeast powder was used as nitrogen source,the extracellular polysaccharide 20 E fractions mainly contained glucose,and the corresponding molar ratio was basically between 50% and80%.When the peptone and yeast extract were used in the case of nitrogen sources,the20 E polysaccharide fractions in the extracellular fluid were mainly composed of the same monosaccharide as the added carbon source.The activity comparison results showed that when the yeast powder was used as the nitrogen source,the activity of 20 E fractions was generally higher than those from the broths fermented with the yeast extract and peptone as the nitrogen sources.When glucose and fructose were used as carbon sources,the activity of 20 E fractions exhibited higher than those from broths fermented with other monosaccharides as carbon sources.The 20 E farctions obtained from broths fermented with xylose and rhamnose as carbon sources did not show obvious activity,which might be related to the structural characteristics of these polysaccharide fractions.The yeast was inoculated in the fermentation broth of G0160 and cultured for different periods to study the effects of yeast growth on the characteristics of G.lucidum extracellular polysaccharide.The results showed that with the prolongation of yeast culture time,the yield of extracellular polysaccharide 20 E fractions gradually decreased,while 70 E fractions(precipitated with 70% ethanol)gradually increased.The monosaccharide compositions in 20 E fractions also showed obvious changes.The ratio of glucose decreased while the ratio of mannose increased with the extending of yeast fermention period,indicating the structure characteristics had changed during this period.The results of activity comparison showed that different polysaccharide fractions obtained from yeast fermented Ganaderma lucidum broths exhibited better activity than those from the broths without yeast culture.The fractions obtained from the broth of yeast culture for 24 h showed the best activity among all the tested samples.