Study On Fermentation Of Polysaccharide And D-mannitol From Cordyceps Mititaris

Polysaccharide and D-mannitol are important active ingredients of Cordyceps militaris. Due to the resources of the natural Cordyceps are scarce, and submerged fermentation is easy to control the products quality. Production of polysaccharide and D-mannitol by fermentation have become a trend today. In this work, the medium constituents and the fermentation conditions for polysaccharide and D-mannitol fermentation by Cordyceps militaris were optimized, and fermentation dynamic models of polysaccharide and D-mannitol were systematically studied. Finally, the extraction of polysaccharide and D-mannitol were optimized by means of orthogonal design. The main results were as follows:1. The liquid culture mycelium of Cordyceps militaris was optimized by means of Box-Behnken designed and analyzed by response surface methodology. The results showed that the predicted model for biomass production was Yx= 9.28+0.64A+0.29B+0.38C+0.21D+0.050AB+ 0.26AC-0.012AD+0.11BC+0.28BD+0.045CD-1.29A2-0.45B2-0.75C2 - 0.72D. Based on the model, the optimum medium for biomass production was sucrose 31.48g/L, peptone 5.84g/L, yeast powder 5.65g/L, and KH2PO4 1.61g/L. Using the best mycelium, the biomass of Cordyceps militaris reached to 9.53g/L. The tested result of biomass yield was very near to the predicted value, suggesting the mathematical model for biomass production of Cordyceps militaris is useful in application.2. Single factor experiments showed that the rotation speed, culture temperatation, initial pH were the key fermentation factors of polysaccharide and D-mannitol. The fermentation conditions of polysaccharide were optimized by means of Box-Behnken designed and analyzed by response surface methodology. The results showed that the mathematical model for polysaccharide(Yp) and D-mannitol(YD)production were YP= 111.65-5.43A+5.86B+0.31C+0.42AB-0.76AC-3.97BC-5.61A2-15.12B2-11.19C2 and YD= 46.64-0.67A-0.84B-0.38C+ 1.71AB-0.66AC+0.26BC-3.48A2-7.41B2-5.20C2. The optimum fermentation condition for polysaccharide was rotation speed 160.65r/min, culture temperatation 22.99℃ and initial pH6.27; while the optimum fermentation condition for D-mannitol was rotation speed 160.55r/min, culture temperatation 22.98℃ and initial pH6.3. The two conditions were not obviously different, then the revised optimum conditions was initial pH6.3, rotation speed 161r/min and culture temperatation 23℃ in order to be applied in practice conveniently. Under this condition, the polysaccharide and D-mannitol of Cordyceps militaris reached to 111.48mg/g and 46.37mg/g respectively. The tested results of the two yields were very near to the predicted values, suggesting the mathematical model for biomass production of Cordyceps militaris was useful in application.3. The fermentation kinetics of polysaccharide and D-mannitol by Cordyceps militaris, was studied. We found that the polysaccharide of fermentation process was analyzed it’s partially copling model, while the production of D-mannitol was it’s copling model. Based on Simgoid model, fermentation dynamics models of polysaccharide and D-mannitol were built. We processed the data by Origin 8.5 and Excel 2003, and built the fermentation dynamics models, namely the biomass growth model, substrate consumption models, polysaccharide and D-mannitol formation models. The results showed that these models could reveal process characteristics of productions.4. The results of the extraction experiments showed that the extraction temperature, solid/solvent ratio and extraction time were the key factors extraction rate of polysaccharide and D-mannitol. The optimum extraction condition for polysaccharide was extraction temperature 70℃, solid/solvent ratio 1:30 and extraction time 3h; The optimum extraction condition for D-mannitol was extraction temperature 90℃, solid/solvent ratio 1:20 and extraction time 60min. Based on the optimization results, we respectively obtained the raw polysaccharide 101.52mg and raw D-mannitol 73.89mg from mycelia, and the yield of raw polysaccharide and raw D-mannitol were respectively up to 10.15% and 7.39%.