Cordyceps militaris medium polysaccharide, method for separating and purifying same, and use thereof

A method for separation and purification of a Cordyceps militaris medium polysaccharide, comprising the following steps:

• (1) extraction of the Cordyceps militaris medium polysaccharide:
• drying the Cordyceps militaris rice medium leftovers, pulverizing and sieving same to obtain a dry powder of the leftovers;
• weighing the dry powder and adding 15-16 times distilled water by mass into same, performing an ultrasonic treatment for at least 30 min, performing a reflux extraction at 70° C. for 1.5 h-2.0 h, pooling the extract solutions after several extractions, and filtering the pooled extract and concentrating same to obtain a polysaccharide concentrate;
• adding 3-4 times of 95% (V/V) ethanol by volume into the polysaccharide concentrate, stirring same, and allowing same to stand overnight at 4° C.;
• after centrifugation, drying the precipitate to obtain a Cordyceps militaris medium polysaccharide extract;
• (2) decoloration of the Cordyceps militaris medium polysaccharide:
• dissolving the Cordyceps militaris medium polysaccharide extract by adding distilled water, adjusting the pH value to 8.0-8.5, adding H2O2 solution dropwisely until colorless, and maintaining the temperature at 50° C.-55° C. for at least 2 h;
• (3) deproteinization by an enzymatic method combined with Sevage method:
• 3-1:
• mixing a papain solution with the Cordyceps militaris medium polysaccharide extract solution, wherein the volume ratio of the two is 1.0:1.5-1.0:1.7, and performing an enzymolysis at 60° C.-70° C. for 2 h-3 h;
• 3-2:
• mixing a Sevage reagent with the solution obtained by the enzymolysis at a volume ratio of 1:5, culturing same with shaking for at least 30 min, then centrifuging for multiple times until no protein is precipitated out;
• and drying the supernatant to obtain a crude Cordyceps militaris medium polysaccharide;
• (4) separation and purification of the Cordyceps militaris medium polysaccharide:
• dissolving the crude Cordyceps militaris medium polysaccharide with distilled water, then loading same to DEAE agarose gel FF ion exchange chromatography column, and eluting same with distilled water to obtain the polysaccharide.