Studies On Submerged Fermentation Of Morchella Esculenta And Polysaccharide Extraction

Morchella escuIenta is one kind of valuable edible and medicial fungus,its nutrition is rich,and the polysaccharide from Morchella esculenta has a wide variety of medicinal activities,such as enhancing body immunity,anti-fatigue and anti-tumor, anti-aging and many other effects.On the area of the submerged fermentation of Morchella esculenta,it studied the impacts of the fermentation conditions on the mycelia biomass,but the impacts of the fermentation conditions on the exopolysaccharide were not studied.And the impacts of many key factors were not studied in the extraction of intracellular polysaccharide and exopolysaccharide.In this study,the experiment studied the materials of Morchella esculentar,using submerged fermentation technology.The impacts of different fermentation conditions on mycelia biomass and exopolysaccharide yield were studied.The process of submerged fermentation of Morchella esculentar was optimized.The impacts of many key factors were also studied in the extraction of intracellular polysaccharide and exopolysaccharide.The process of extraction of polysaccharide and exopolysaccharide was optimized,too.It was hoped to provide a theoretical and scientific basic for the further studies of fermentation products,especially the exopolysaccharide from submerged fermentation of MorcheIla esculentar.The results were as follows:1.The optimal ratio of carbon sources,nitrogen sources and inorganic salts,was identified through a single factor screening test and the two orthogonal tests, accessing to the mycelia biomass and exopolysaccharide yield.The optimal medium ratio of the submerged fermentation was as follows:corn powder 4.0%,glucose 1.0% soybean meal 2.0%,yeast extract 0.3%,KH₂PO₄ 0.2%,MgSO₄ 0.1%CaSO₄ 0.1%.2.The impacts of different factors on the mycelia biomass and exopolysaccharide yield,as temperature,pH,liquid volume and inoculum amount, rotation speed,,were studied on the basic of the optimal fermentation medium. Results of the test showed that the optimal culture conditions was as follows:24℃, initial pH 5.8,the liquid volume 100ml/250ml,inoculating amount 10.0ml,rotation speed 140r/min.3.It was found that the mycelia biomass was positively correlated with the exopolysaccharide yield,was negative correlated with the content of amino nitrogen, and had some relevance with the residual sugar concentration and the pH.In the 108h, mycelia biomass reached the maximum value,the exopolysaccharide yield reached the maximum value nearly,and the content of residual sugar and protein reached the minimum value nearly.It could be identified that the growth of mycelia had reached the best condition,and determined 108h around for the end time of fermentation.4.Four factors,extraction ratio,time,temperature and ethanol concentration, were studied in the process of polysaccharides extraction from mycelia of Morchella esculenta.The suitable process was determined as follows:80℃,150min,add water of 40 times of mycelia,and then precipitated at a final 75%ethanol at 4℃overnight. The pellets were harvested by centrifuge,washed several times with 95%ethanol,and the polysaccharides from mycelia could be gained.Four factors,concentration ratio,temperature,ethanol concentration and pH, were studied in the process of exopolysaccharide extraction.The suitable process for exopolysaccharide extraction was determined as follows:pH of ferment liquid was changed to 6.0,concentrated to 1/3 volume at 80℃and then precipitated at a final 75%ethanol at 4℃overnight.The pellets were harvested by centrifuge,washed several times with 95%ethanol,and the exopolysaccharide could be gained.