Research On Fast Extraction And Controlled Degradation Of Polysaccharides From Tremella

Tremella is not only an edible fungus with extremely high nutritional value,but also a precious herb with significant medicinal effects.At present,the traditional hot water extraction method is most widely employed to extract polysaccharide from Tremella.However,this method has the drawbacks of long processing time,high energe consumption and low yield.To extract the water-soluble Tremella fuciformis polysaccharide more rapidly and more efficiently,a novel extraction method by wet mashing was studied in this thesis.In addition,Tremella polysaccharide is large in molecular weight,complex in structure,poorly soluble in water and very strong in viscosity after dissolving,which will greatly limit its wide applications.Therefore,in this thesis,the controlled degradation of Tremella fuciformis polysaccharides by the H₂O₂ method was studied to obtain the polysaccharides with different molecular weights.Also,the in vitro antioxidant,moisture-absorption and moisture-retention abilities of degradation products with different molecular weights were systematically studied.The main contents and conclusions of this thesis are summarized as follows:By using single factor test and orthogonal test,we optimized the fast extraction process of polysaccharide from Tremella fuciformis,The optimum conditions were as follows: material-liquid ratio of 1:50?g/ml?,time 7min,temperature 80 ?.Through the range analysis and variance analysis,the influence sequence selected three factors on extraction rate were the ratio of material to liquid,time,extraction temperature.Under the optimal extraction conditions,the yield of polysaccharides was up to 40.57%,and was 2.20 times than traditional extraction by hot water;the extraction duration was reduced to one-sixtieth of traditional extraction by hot water.We studied three methods including to remove protein by using the Tremella polysaccharides,The optimal process for the removel of protein was papain-isoelectric point method,and the results showed that the optimal removement conditions were as follows: pH = 6,enzyme dosage 2%,temperature 50 ?,reaction time 2 hours.Under this conditions the removel rate was up to 91.23%,and the loss rate of polysaccharide was up to 8.57%.There was no proteins and nucleic acids in TP from the result of ultraviolet spectrum.Tremella polysaccharides was obtained through the fast extraction in the optimium conditions,with deproteinized and ethanol subsided.Tremella polysaccharides was purified by DEAE-52 ion-exchange column chromatography to gain a acidic polysaccharide eluted by 0.2 mol/L NaCl,which named TP.The content of polysaccharide in TP had been detected,that was 91.83%.Through the gel permeation chromatography,the number average molecular weight mass of TP was measured,that was1.70×104 kDa,and the peak time for the single peak symmetry of TP was 17.583 min.By using single factor test,we optimized the process of controlled degrading macromolecular TP,The optimum conditions were as follows: hydrogen peroxide concentration 1.5%,time 40 min,temperature 60 ?,Thus the molecular weight of TP could be degraded from1.70×104 kDa to 4.3 kDa.Four different low-molecular-weight soluble Tremella polysaccharides?TP1?TP2?TP3?TP4?were prepared by the controlling the degradation condition,which were respectively molecular weights of 1869.6 kDa?123.1 kDa?31 kDa?4.3 kDa.Studied on the antioxidant activities of four Tremella polysaccharides with different molecular weight showed that they all had the antioxidant activities in different antioxidant systems,and the Tremella polysaccharides with molecular weight 31 kDa performed the strongest antioxidant acitivities in three antioxidant systems.The moisture-absorbing property and moisture-retention property of Ttremella polysaccharides with different molecular weight were also studied in this paper.It showed that the molecular weight of Tremella fuciformis polysaccharides has a significant effect on the hygroscopicity and moisturizing properties of Tremella polysaccharides.The lower the molecular weight of Tremella polysaccharides,the better the hygroscopicity is.The higher the molecular weight of Tremella polysaccharide degradation products,the better the moisturizing performance.In this thesis,the optimum process of rapid extraction of Tremella fuciformis polysaccharide by wet mashing was determined.The yield of polysaccharide was 2.2 times higher than traditional extraction by hot water;the extraction duration was reduced to one-sixtieth of traditional extraction by hot water.In addition,this paper identified the optimum process of removing the protein by using Isoelectric point – Enzymatic method deproteinization and identified the optimum process of the controllable degradation of Tremella polysaccharide,and obtained different molecular weight polysaccharides of Tremella fuciformis.