Study On Fermentation Preparation,rheological Properties And Application Of Schizophyllum Commune Polysaccharide

Schizophyllum commune（S.commune）is a valuable edible and medicinal fungus.Polysaccharide,as its main high-efficacy component,has a variety of biological activities and unique physicochemical properties,and has potential applications in medicine and daily chemical fields.Further increasing polysaccharide yield is the basis of its large-scale application.Liquid fermentation is an efficient way to prepare edible and medicinal fungal polysaccharides,which can obtain both fermentation broth polysaccharide（extracellular polysaccharide）and mycelium polysaccharide（intracellular polysaccharide）at the same time.The multistage structure and rheological behavior of polysaccharide affect its application prospect.In this study,the optimum fermentation promoter for polysaccharides production by liquid fermentation of S.commune was selected and the adding process was optimized,and the mechanism of high yield polysaccharides was further elaborated.The pure polysaccharide was purified from fermentation broth and mycelium by column chromatography,and its structure was analyzed.The rheological properties of polysaccharide and its effect on texture modification of common liquid food were analyzed.An emulsion system stabilized with S.commune fermentation broth was established.The main findings are as follows:（1）Tween 80 was identified as the most suitable promoter for promoting polysaccharide production of liquid fermentation of S.commune.Changes in morphology and microstructure of mycelium,increased content of energy-supplying substances and up-regulated expression of key enzyme genes in polysaccharide synthesis were the reasons for Tween 80 promoting polysaccharide high yield.By comparing the effects of different surfactants on polysaccharide production,Tween 80 was identified as the most suitable fermentation promoter.Adding 1 g/L Tween 80 to the culture medium at 0 h made the yields of extracellular polysaccharide,intracellular polysaccharide,total polysaccharide and biomass reach 3.77 g/L,200.80 mg/g,337.69 mg/g and 25.78 g/L,which increased by 37.17%,56.73%,40.76%and 7.06%compared with the control,and fermentation cycle is shortened.After the addition of Tween 80,the mycelial pellets size decreased,the cell membrane permeability and intracellular ATP level increased significantly,the cell wall thickness and the content of chitin andβ-1,3-glucan increased,and the transcription levels of phosphoglucomutase genes pgm1,pgm2 andβ-1,3-glucan synthase genes bgs1 and bgs2 were significantly upregulated.（2）The pure components of S.commune fermentation broth polysaccharide and mycelium polysaccharide were extracted and purified.The structural analysis results showed that the main components wereβ-glucan with triple-helix rigid chain.S.commune fermentation broth polysaccharide（SCFP）and mycelium polysaccharide（SCMP）were obtained from fermentation broth and mycelium,respectively.SCFP and SCMP were purified by DEAE-Purose^TM Fast Flow ion exchange column and Purose^?Fast Flow gel column to obtain four pure polysaccharide components:SCFPA（86.50%）,SCFPB（13.50%）,SCMPA（83.44%）and SCMPB（16.56%）.The molecular weights of the four pure polysaccharides were3.465×10⁶ g/mol,3.307×10⁶ g/mol,3.741×10⁶ g/mol and 4.193×10⁶ g/mol,respectively.SCFPA,SCMPA and SCMPB were rigid chainβ-glucans,SCFPA and SCMPA had triple-helix conformation,and SCFPB was triple-helix rigid chain heteropolysaccharide.SCFPA consists of 1-Glcp,1,3-Glcp and 1,3,6-Glcp,while SCMPA consists of 1-Glcp,1,3-Glcp,1,4-Glcp,1,3,4-Glcp and 1,3,6-Glcp.（3）Rheological studies determined that S.commune fermentation broth polysaccharide and mycelium polysaccharide aqueous solutions were shear-thinning fluids with high viscosity and have elastic-dominated viscoelastic behavior at low concentrations,and exhibit good temperature stability.Both polysaccharides can improve the texture of common liquid foods.The steady-state shear test results showed that the shear-thinning characteristics of SCFP and SCMP aqueous solutions are positively correlated with the concentration,and the critical concentration of the transition from dilute solution to semi-diluted solution is 0.275 g/L and 0.356 g/L,respectively.The thixotropy degree of polysaccharide aqueous solution increased with the increase of polysaccharide concentration.The viscosity curves of SCFP and SCMP aqueous solutions almost coincide at 10–70℃,and the maximum flow activation energy are 3.251 k J/mol and 3.951 k J/mol,respectively.In the test concentration range（1.25–7.5 g/L）,the two polysaccharide aqueous solutions showed a“solid”viscoelastic behavior,and the strength increased with increasing concentration and decreasing temperature.SCFP and SCMP aqueous have creep-recovery properties.Theη₅₀ and yield stress values of coffee and fruit tea thickened with SCFP or SCMP are higher than that of polysaccharide aqueous solution.（4）Oil-in-water emulsion was prepared directly with S.commune fermentation broth as continuous phase.S.commune fermentation broth inhibited lipid oxidation in the emulsion and increased the retention rate ofβ-carotene and curcumin.The bioavailability ofβ-carotene was lower than that of curcumin after simulated gastrointestinal digestion in vitro.S.commune fermentation broth-based emulsion（SCFBe）was prepared by high-speed homogenization method.SCFBe had good stability when polysaccharide concentration was as low as 3 g/L.SCFBe showed better stability than S.commune fermentation broth polysaccharide-based emulsion（SCFPe）at 60℃.SCFB effectively inhibited the production of lipid hydroperoxides and malondialdehyde,and increased the retention rate ofβ-carotene and curcumin.The bioaccessibility ofβ-carotene and curcumin ranges from 11.18%to 12.28%and31.45%to 33.00%after simulated gastrointestinal digestion in vitro of SCFBe containing different concentrations of polysaccharides.