Study On Sulfated Modification Of Exopolysaccharides From Fungifermentation And Its Biological Activity

In this experiment, Pleurotus geesteranus, Pleurotus eryngii (DC. etFr.)Quèl., Funalia trogii(Berk.) Bondartsev&Singer and Strophariarugoso-annulata Farlow apud Murrill were selected as experimental materials. Themethod of submerged fermentationwithshake flask culture was used to getexopolysaccharides(EPS) from the four fungi. The four different EPS were sulfatedmodified to obtain sulfated exopolysaccharides(S-EPS).The structure and thermalstability of EPS and S-EPS were preliminarilyanalyzed by FT-IR and TG.Thebiological activitiesincluding antioxidant activity and antibacterial activity in vitro ofEPS and S-EPS were investigated. The results were as follows.1.The sulfate group content in S-EPS of P.geesteranus, P.eryngii, F.trogii andS.rugoso-annulata respectively were15.4%,17.47%,10.08%,17.95%, thesubstitution degree respectively were1.53,1.99,0.75,2.12.2. The FT-IR spectra graphs of EPS and S-EPS showed that there werecharacteristic absorption peaks of EPS matrix and sulfation of the four S-EPSof fungi.3. TheTG analysis graphs of EPS and S-EPS showed that the temperature rangeof the thermal cracking reaction of the four EPS was100℃to400℃and the TGcurvebegan to flatten after480℃.The four S-EPS reached the maximum weight lossrate between200℃and240℃, the TG curvebegan to flatten after480℃, but the TGcurverapidly wentdown again after680℃.4. The S-EPSof P.eryngiiand S.rugoso-annulatahad the strongest clearancecapacity of·OH radical, the clearance ratio was70%when the mass concentration ofS-EPS was10g/L. The·OHradical clearance ratio of the S-EPSof P.geesteranusandF.trogii was about30%. The·OHradical clearance ratio of the EPSof the otherthree fungi was about35%, otherwise, the EPSof P.eryngii hadn′t the clearancecapacity of·OH radical. The·DPPH radical clearance ratio was between20%and35%when the mass concentration of EPS and S-EPS was10g/L.5. The EPSof P.geesteranus, P.eryngii and F.trogii had weakerantibacterialactivity in terms of Escherichia coli, Bacillus subtilis and Staphylococcus aureus. Theantibacterial ratios to the three bacterias of the EPSof S.rugoso-annulatawere morethan90%. The S-EPSof the four fungi had strongantibacterial activity, the antibacterial ratios to the three bacterias of the four S-EPSwere all more than95%.