Changes in enzyme activity,nutritional components and antioxidant activity of Lentinula edodes stalk substrate during solid-state fermentation of Poria cocos
Poria cocos was cultured on the solid medium using Lentinula edodes stalk as the sole sub-strate to study whether the mycelia of P.cocos can ferment and utilize L.edodes stalk substrate and im-prove its nutritional value and biological activity.The activity of key enzymes,the components of main nu-trient,and the antioxidant activity of water extracts from the fermented substrate during solid-state fermen-tation of P.cocos were measured.The results showed that the activity of cellulose exonuclease reached 46.14 U/g at the 6th day of fermentation,then rapidly decreased to 17.15 U/g,and remained basically un-changed at the 18th day of fermentation as the process of fermentation progressed.The activity of carboxy-methyl cellulase and xylanase reached 77.70 U/g and 74.23 U/g at the 12th day of fermentation,and then gradually decreased.The activity of β-glucosidase reached 75.06 U/g at the 18th day of the fermentation and then gradually decreased.Compared with the unfermented L.edodes stalk substrate,the content of to-tal sugar,soluble protein,and insoluble dietary fiber in the fermented L.edodes stalk substrate significantly decreased,but the content of reducing sugar,polysaccharides,total phenols,total flavone,amino nitro-gen,and soluble dietary fiber significantly increased.The antioxidant activity of water extracts from the fer-mented substrate was significantly increased.The scavenging rate of DPPH radical and hydroxyl radical in-creased by 97.75%and 38.15%,compared to the 0 day of fermentation.It is indicated that P.cocos can ferment L.edodes stalk,alter the composition of nutrient in L.edodes stalks,and that the fermented sub-strate has good ability to scavenge free radicals.
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