| For millennia, the edible and medicinal fungi have been used as pharmaceutical products in China. It is well known that the biologically active substances derived from the fungal species, especially polysaccharides, are regarded as biological response modifier (BRM) to stimulate human immune function. At present, edible and medicinal fungi comprise an important source for modern medicine to pick out the powerful new medicine with antitumor and immunostimulating properties. Whereas, the three edible and medicinal fungi, i.e. Boletus sp. ACCC 50328, Pholiota squarrosa AS 5.245 and Clitocybe sp. AS 5.112 was studied firstly concerning their submerged fermentation and antitumor effect, the Clitocybe sp. AS 5.112 strain was screened lastly because of its higher antitumor effect.In this paper, the Clitocybe sp. AS 5.112 strain was further investigated systemically with respect to its processes optimization of submerged fermentation, antitumor activity against Sarcoma 180 as well as the correlation of chemical structure and bioactivity. The main results are as follows:1. Mycelium growth and polysaccharide accumulation in submerged fermentation by Clitocybe sp. AS 5.112 are strongly affected by many external and internal factors. In the present investigation, the methodology of Plackett-Burman (PB) was undertaken to screen the key factors rapidly from the related twenty factors, i.e., glucose, fructose, maltose, yeast extract, tryptone, K2HPO4, KH2PO4, (NH4)2SO4, NaNO3, FeSO4, MgSO4, MnCl2, ZnCl2, FeCl3, CuSO4-5H2O, vitamin Bj, initial pH, fermentation temperature, time and volume of medium. By analyzing the statistical regression and the prediction profiler, glucose, yeast extract, KH2PO4, FeSO4, MgSO4, FeCl3, initial pH, fermentation temperature and time are found to be the most important factors for mycelium growth of Clitocybe sp. AS 5.112, while glucose, yeast extract, tryptone, K2HPO4, NaNO3, vitamin B1 and volume of medium for exopolysaccharide produced by this strain.2. Based on the results of our previous Plackett-Burman design, five-level five-factorfull-factorial central composite design was employed in the present study to optimize the levels of the chosen variables, which significantly affect the yield of extracellular polysaccharide and mycelium biomass in submerged fermentation using Clitocybe sp. AS 5.112, i.e. glucose, yeast extract, tryptone, NaNO3 and MgSO4. By analysis of the response surface contour plots generated from the quadratic regression equation, the effects of the individual variable as well as the mutual interactions between variables were extensively studied. The result suggest that the concentration values of glucose, yeast extract, tryptone, NaNO3, and MgSO4 were in the following ranges (g L-1): 14.00 -17.15 4.10 ~ 6.00, 1.63 ~ 2.40 2.00 - 3.25 and 0.92 ~ 1.60 respectively, the yield of extracellular polysaccharide could reach over 1045.52 ug ml-1, while the above-mentioned variables were in (g-L-1) 19.30 ~ 24.00, 3.00 ~ 4.52, 1.00 - 2.06, 2.00 - 3.02 and 1.41 ~ 1.60 respectively, 6.63 mg-ml-1 or more mycelium biomass was harvested. By solving the model equation using appropriate statistic methods, the optimum concentration levels were determined (g-L*1): under conditions of glucose, 14.00; yeast extract, 5.11; tryptone, 2.07; NaNO3, 2.00 and MgSO4,1.28, the predicted yield of extracellular polysaccharide by Clitocybe sp. AS 5.112 was 1081.80 ug per milliliter of culture liquor, while the above factors were 24.00, 3.23, 1.52, 2.36 and 1.60, respectively, the maximum mycelium biomass was 6.81 mg per milliliter of culture liquor. In order to obtain the maximum yields of extracellular polysaccharide and mycelium biomass at the same time, the optimal concentrations of glucose, yeast extract, tryptone, NaNO3 and MgSO4 would be located at 21.74, 4.33, 1.65, 2.45 and 1.50, respectively. In this situation, 1011.30 microgram of extracellular polysaccharide and 6.66 milligram of mycelium biomass were gained simultaneously. The validation data under different experimental levels h...
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