Method for preparing antioxidant active polysaccharides from oak culture medium

The invention discloses a method for preparing antioxidant active polysaccharides from an oak culture medium. The antioxidant polysaccharides are extracted from the oak culture medium obtained after Ganoderma lucidum sporocarps are harvested. The preparation method of the antioxidant polysaccharides comprises the following steps: crushing the oak culture medium obtained after cultivating the Ganoderma lucidum sporocarps, performing extraction with hot water, cooling obtained filtrate to room temperature, carrying out reduced pressure concentration, adding ethanol for precipitation, carrying out centrifugal separation, recovering the ethanol, re-dissolving the precipite to obtain a crude polysaccharide solution, removing proteins by a Sevag technology, taking the obtained upper water phase,and carrying out freeze drying to obtain the polysaccharides with antioxidant activity. The polysaccharides are a yellowish-brown powder, the extraction yield is (3.04-5.65) g/100 g oak culture medium dry weight, the purity