Abstract:The content and bioactivity of extracellular polysaccharides from 4 strians of Agaricus blazei were studied.Extracellular polysaccharides were extracted by submerged liquid fermentation.The content of polysaccharides was determined by phenol-concentrated sulfuric acid method and 3，5-dinitrosalicylic acid（DNS）method.The inhibition of bacteria and alpha-amylase were studied by filter paper diffusion method and spectrophotometry respectively.The antioxidant activity of polysaccharides in vitro was investigated by detecting the scavenging rate of DPPH free radical，ABTS+free radical and·OH free radical.The antimicrobial activity of exopolysaccharides from strain JS06 was higher than that of the other three strains of Agaricus blazei，and the effect on Staphylococcus aureus was the best.The IC50 of strain JS01 to alpha-amylase was 2.425 mg/mL，which was superior to other three strains of Agaricus blazei.The scavenging rates of DPPH，ABTS+ and hydroxyl radicals of four Agaricus blazei strains increased with the increase of mass concentration.When the mass concentration reached 1.0 mg/mL，the scavenging rate of strain JS01 to ABTS+ radicals was 83.06 %，higher than that of the other three strains.The scavenging rates of DPPH free radical and hydroxyl free radical by JS06 were 96.47%and 99.71%respectively，which were higher than the others，and the scavenging rate of hydroxyl free radical was higher than that of VC.The results showed that the extracellular polysaccharides of the four Agaricus blazei strains had bioactivity and potential medicinal value.