| In the present study, the effects of different kinds of aqueous herbal extracts on submerged fermentation of Paecilomyces cicadae were investigated, and the structural characterizations of an intercellular polysaccharide obtained from the mycelia of P. cicadae were analyzed. Therefore, this dissertation was composed of two parts as follows:Part Ⅰ:The effects of different kinds of herbal extracts on submerged fermentation of P. cicadae were studied.1). The impacts of different aqueous extracts of herbs on biomass, the yield of exopolysaccharide and intracellular polysaccharide as well as its antioxidant activities were studied by the means of adding these water extracts to culture medium of P. cicadae in submerged fermentation process. Results showed that the positive effects of aqueous extracts of Astragalus membranaceus, Coix lachryma-jobi, Lycium barbarum on biomass, the synthesis of exopolysaccharide and intracellular polysaccharide separately were the most remarkable ones, which increased by 135.82%,48.90%,137.18% compared to the control, respectively. While the aqueous extracts of Flos Lonicerae and Crataegus pinnatifida were not beneficial to fermentation of P. cicadae. It was indicated that the activities of metabolites were improved significantly by the aqueous extract of Lycium barbarum, the scavenging ability of DPPH radical of exopolysaccharide and intracellular polysaccharide were 1.17 folds and 1.38 folds of those of the control, respectively.2). Synthesizes these results, aqueous extract of Lycium barbarum was selected as the optimum herb ingredient for submerged fermentation of P. cicadae, and its proposed dosage was 10 g/L.Part Ⅱ:The structural features of an intercellular polysaccharide of P. cicadae were characterized.1). A yield of 4.2% of a water-soluble crude polysaccharide (PCIPS) was obtained from the mycelium of P. cicadae by undergoing a set of process as extraction with hot water, precipitation separation with alcohol, deproteinization, desalination, and then purified by DEAE-Sepharose Fast Flow chromatography and Sephacryl S-100 gel filtration chromatography. 2). The structural features of a neutral heteropolysaccharide (PCIPS2), obtained from the mycelia of P. cicadae, were investigated by the analysis of high performance liquid chromatography (HPLC), infrared spectroscopy (IR), methylation,1D/2D NMR spectroscopy.The results showed that PCIPS2 was mainly composed of mannose, rhamnose, glucose, galactose in a molar ratio of 48.21:6.89:2.37:1.0, and had a backbone of 1,4-linked β-L-Rhap residues and 1,6-linked a-D-Manp residues with branches comprised of terminal a-D-glucose, 1,4-linked α-D-Galp residues linked to O-3 of 1,6-linked a-D-Manp residues.3). Furthermore, its chain conformation was determined by size-exclusion chromatography combined with multi-angle laser light scattering, refractive index and online viscometry (SEC-MALLS-RI-VIS). The values of weight average molecular weight (Mw), radius of gyration (<S2>z1/2), hydrodynamic radius (Rh) and intrinsic viscosity ([η]) for PCIPS2 were analyzed to be 3.09×104 g/mol,7.8 nm,3.6 nm and 8.5 mL/g. The structural exponent a of 0.57 indicated that PCIPS2 existed as a flexible chain conformation with a coil-like structure in 0.1 M NaNO3 at 25 ℃. In term of known theory for worm-like chains, the model parameters for PCIPS2 were as following: molar mass per unit contour length (ML)=379 nm-1, persistence length (q)=0.74 nm and hydrodynamic diameter of cylinder (d)=0.82 nm, which were further evidenced by atomic force microscopy (AFM). This work provided valuable information for better understanding of the relationship between the structure-function of PCIPS2 in health food fields. |
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