The Selection Of Excellent Strain Of Grifola Frondosa And Its Characteristic Research Of Liquid Fermentation

An excellent strain of Grifola frondosa for liquid fermentation from five strains of Grifola frondosa which are planting extensively at present was screened out depending on the capability of generating polysaccharides, and the conditions and characteristics in liquid fermentation of which were studied.The phylogenetic relationship of tested strains was indentified by the methods of antagonistic test and catalase isoenzyme test. The result of antagonistic test indicated that the antagonistic line has appeared in the middle of all two-two combined plates, preliminary suggested that the tested strains are different strain. And the catalase isoenzyme test showed that different strain has differences in the zymogram type of catalase isoenzyme, and the same zymogram type exactly was not existed. Three clear bands were checked out in different place of Rf value, whose relative mobility were Rf_E1 = 0.214, Rf_E2 = 0.576 and Rf_E3 = 0.782. Strain Gf-2 missed a band in the place of Rf_E2, and strain Gf-5 missed a band in the place of Rf_E3, which put out large difference with other strains, so strain Gf-2 and Gf-5 have the distant phylogenetic relationship with other tested strains.The comparative test on the plate solid culture showed that strain Gf-5 has the faster mycelial growth speed and the better vigor, strain Gf-1, Gf-3 and Gf-4 have an ordinary performance, while strain Gf-2 has the worst performance compared with strain Gf-5. The comparative test of high-temperature tolerance suggested that strain Gf-2 and Gf-5 could sprout new mycelial quickly after the treatment of high temperature, so the high-temperature tolerance of strain Gf-2 and Gf-5 is better than other tested strains. However, the comparative test on the capability of producing polysaccharides of tested strains in liquid fermentation indicated that strain Gf-3 has the smallest diameter of mycelia pellet and the highest biomass of mycelia while culturing in the flask liquid, and the output of extracellular polysaccharides, intracellular polysaccharides and total polysaccharides of whose reached to 11.07mg/100mL, 28.68mg/100mL and 39.75mg/100mL respectively, higher than the other strains. Thus strain Gf-3 is the most suitable strain for liquid fermentation. And then, the quality and identification of screened strain Gf-3 were verified through the fruiting test.The optimization test on the culture medium of screened strain Gf-3 for liquid fermentation suggested that glucose and peptone were the best carbon and nitrogen source. And the concentration of glucose 34.62g/L and peptone 2.59g/L were suited for liquid fermentation via response surface methodology. The optimization test on the culture conditions of screened strain Gf-3 for liquid fermentation suggested that initiative pH 6.0, the volume of shake flask 100～150mL/500mL, put in the seed of culturing 7d according to inoculation volume 10% (V/V), and finish the fermentation after 6d of cultivation under the conditions of 26℃and rotation rate 150～200r/min.The test of liquid culture in fermentor of screened strain Gf-3 showed that lag phase of fermentation existed in the first 48h, log growth phase between 48h and 132h, stationary phase between 132h and 168h, and decline phase after 168h. The pH value gradually declined while the mycelial biomass and extracellular polysaccharides gradually accumulated throughout the fermentation process, and the synthesis of extracellular polysaccharides are coupled with the growth of mycelia. Finish the fermentation at the later of stationary phase and just before the myceliolysis.