| SPG(Schizophyllan) is a functional polysaccharide fermented by Schizophyllum, with improving immunity, anti-tumor and other biological activities. Schizophyllum has strong decomposition ability of fiber matrix, can make use of agro-processing by-products (corn cob, wheat bran, etc.) to produce SPG to achieve waste to treasure. In this study, we chose high SPG yield strain Schizophyllum, optimized extraction, purification process of SPG, studied irradiation modification of SPG, and functional activity of natural and irradiated SPG, investigated the prospects of production and application of SPG, provided theoretical and experimental evidences for realization of industrialization of SPG.Four Schizophyllum strains collected were screened, the results showed the highest SPG yield strain was No. ACCC51174 strain from Northeast of China, its yield achieved 4.84±0.33%, it was higher than other strains (p<0.05).Hot water extraction method was used to extract SPG, we investigated extraction temperature, time, solid to liquid ratio and pH on SPG extraction rate. Orthogonal experimental design was used to optimized extraction process, the optimum conditions was temperature 90℃, solid to liquid ratio 1:24(g/ml), pH11, time 60min, the SPG extraction rate was 4.93±0.02%.On the decolorization process of SPG, determined to use D301-F resin and No.10 activated carbon for decolorization, response surface method (RSM) was used to optimized decolorization process of resin, the optimum condition were: amount of resin 28.4ml/100ml extraction, temperature 76.8℃,pH5.32,the decolorization rate was 80.28%. Orthogonal experimental design was used to optimize the decolorization process of activated carbon, the optimum condition were: amount of activated carbon 3.0%, temperature 70℃, pH4.0, decolorization rate was 89.24%.Emulsification of SPG was effected by the concentration, pH and temperature. Emulsification capacity (EC) and emulsification stability (ES) of SPG decreased with increasing concentration, but these were still higher than xanthan gum. EC decreased from 88.30% to 84.48%. ES decreased from 93.42% to 85.71%.With increasing pH (2-8) EC of SPG first increased and than decreased, at pH6 was the maximum EC, reached 79.96%. ES of SPG did not change significantly. EC of SPG increased with increasing temperature, became stable after 60℃, reached 91.23%. The ES did not change significantly with temperature.Rheological properties of SPG solution were affected by concentration, pH value, electrolytes and sucrose. The higher was the concentration the more obvious shear thinning behavior. Under pH 10 viscosity of SPG increased, other pH values (2-8), the viscosity is lower than the natural pH value. Heat stability of pH 10 was the worst, and that of pH 4 was the best. NaCl reduced the viscosity of SPG solution, but CaCl2 and sucrose made no significant change of viscosity.Irradiation could really degrade and solubilize SPG in fermented corn cob, the effect was affected by moisture content and irradiation dose. The yield of SPG increased with increasing of moisture content; when the moisture content exceeds 45%, the yield increased significantly (p<0.05), at 60% moisture content and irradiation dose 10kGy the extraction rate was maximum, reached 7.95%. Zero shear viscosities (η0) of irradiated SPGs were significantly lower than the sample without irradiation (p<0.05); at different moisture contents, along with irradiation dose changes, change trends ofη0 were different. Change curves of the storage modulus G'and loss modulus G"intersected at one point, according to the position of the intersection the change trends of molecular weight can be inferred. Its analysis outcomes were consistent with that ofη0.Molecular and particle size of irradiated SPG decreased obviously. Results of Multi-angle laser light scattering showed that 10kGy irradiated SPG mainly contains three molecular weight fractions, respectively, 2.972×105Da, 4.770×104Da and 1.261×104Da, mass percentage of 60.5%, 21.9% and 17.6%, were lower than the reported natural SPG molecular weight (6-12×106Da). Results of laser particle size analyzer showed that SPG without irradiation contains three particle size fractions, respectively 18.58μm, 8.80μm and 5.02μm, the volume percentage of 55.8%, 23.4% and 20.8%; and the 10kGy irradiated SPG contains only one component size of 0.092μm. These reflected the radiation degraded SPG significantly.Anti-tumor immune activity of natural and 10kGy irradiated SPG was investigated. The results showed that tumor inhibition rate, delayed type hypersensitivity (DTH) induced by sheep red blood cells (SRBC) and spleen cell-mediated quantitative hemolysis of SRBC Quantitative hemolysis test sub-luminosity (QHS) value were met or exceeded the positive control, indicating the two samples can be activated mouse immune system, but there was no significant difference between them (p>0.05). |
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