Study On Optimization Of Fermentation Conditions And Flavor Components Of Boletus Edulis

Boletus edulis,an ectomycorrhizal fungus,also called "dajaogu";it is popular with people all the world for heavy flavor and delicious testing.Up to now,this kind of mushroom still can't artificial cultivation,which made wild mushroom products cannot meet people's demand.Mushroom liquid fermentation could get lots of mycelium and fermentation products,it's has bright supplying prospect.In this thesis,the submerged fermentation conditions for Boletus edulis were optimized by using response surface methodology(RSM).Meanwhile,the flavor components in the fruiting bodies and fermentation products of B.edulis were investigated.The optimal basal medium was obtained through the one-factor-at-a-time procedure.The optimal nitrogen source,carbon source,and nitrogen source were soybean powder,maltose and yeast extract,with the addition of sunflower oil at 12ml/l.The single-factor experiments results indicated that the optimal temperature was 28℃, pH at 6.0,rotation speed of 180r/min and the broth content of 60ml in 250ml flask.Based on the formal results,maltose,soybean power and yeast extract were chosen as the key factors to optimized by RSM.The model was obtained by regression of the experimental results.The fit significant of the model was evaluated by t-test and F-test. The optimal conditions were predicted by the model as follows:maltose 20g/l,yeast extract 7g/l,soybean powder 25g/l,sunflower oil 12ml/l,temperature 28℃,pH 6.0, rotation speed 180r/min,broth content 60ml,KH₂PO₄ 5g/l,MgSO₄.7H₂O 3g/l,CaCO₃ 2g/l, and VB₁ 10mg/l.The maximum predicted yield of mycelia biomass was 41.17g/l,which was in good agreement with the experimental value.After the investigation of the flavor components,the results indicated that 1-octen-3-ol (19.52%),1-Octen-3-one(11.98%)and other eight carbon components were the major volatile compounds in dry B.edulis.The samples treated withβ-glucosidase were better than the untreated ones by sensory evaluation with the significant level at 5%.17 new components emerged(16.63%)afterβ-glucosidase hydrolysis indicating thatβ-glucosidase could enhance the flavor of the B.edulis.3-hydroxy-2-butanone(95.15%)is the main flavor component in the fermentation products of B.edulis.Afterβ-glucosidase hydrolysis,20 new components emerged accounting 3.36%of the total components.Also,the samples treated withβ-glucosidase were better than the untreated ones by sensory evaluation with the significant level at 1%. These results indicated thatβ-glucosidase could enhance the flavor of the fruiting bodies and fermentation products of B.edulis.