| Highland barely 25 is a Tibetan alfalfa variety with high?-glucan bred in 2002,and its?-glucan content can reach 8.62%.?-glucan is a soluble dietary fiber that cannot be digested by human gastrointestinal enzymes and can reach the colon and affect the composition and function of the intestinal flora.This effect is related to the physicochemical properties of?-glucan.No related research has been found on the physicochemical properties of Highland barely 25?-glucan,and its influence on the intestinal flora has yet to be discovered.In this experiment,the preparation of the?-glucan was carried out using Highland barely 25 as a raw material,and the purification results were verified by purity and molecular weight measurement,and the basic physical and chemical properties were determined.The basic chemical structure of?-glucan was studied by monosaccharide composition,nuclear magnetic resonance,Fourier transform infrared spectroscopy,atomic force microscopy and field emission scanning electron microscopy.The effects of intestinal flora of?-glucan were studied by in vitro fecal fermentation and 16S rDNA high-throughput sequencing.The effect of in vitro fermentation of?-glucan on microbial metabolites was studied by gas chromatography.The research results are as follows:?1?The purity of crude?-glucan prepared by alkali extraction and alcohol precipitation method can reach 68.35%,and the purity of polysaccharide can reach 90.61%after purification by DEAE-Sepharose Fast Flow and Sepharose 6B,which can meet the purity requirements of subsequent tests.At the same time,the molecular weight measurement results are single peak and the peak shape symmetric,indicating that the molecular weight distribution is uniform,and the molecular weight is 34.456 KDa.The solubility and viscosity were 41.26%and 1.01 mm2/s.?2?The results of monosaccharide composition,Fourier transform infrared spectroscopy,nuclear magnetic resonance,atomic force microscopy and field emission scanning electron microscopy of the purified barium?-glucan showed that the barley?-glucan was mainly composed of glucose.And glucose constitutes a sugar chain by?-1,3-Glup and?-1,4-Glup linkage.The green?-glucan solid particles have the smooth surface,a sheet shape,a long column shape,and an elliptical shape,and there is a certain cross-linking in the solution.?3?The 16S rDNA sequencing structure found that the proportion of Bacteroidetes and Firmicutes bacteria involved in the production of the butyric acid and the propionic acid in vitro fermentation of?-glucan was increased.At the level of the phylum,the proportion of Bacteroides and Firmicutes increased,but the Proteobacteria decreased.At the level of the family,the Bifidobactatiaceae and the Prevotellaceae is elevated.At the genus level,the Enterobacter decreased and the Prev-otella<sub>9 was elevated.The differential analysis of the KEGG metabolic pathway showed that there were 24 metabolic pathways involved in the in vitro fermentation blank group and the barely?-glucan group,in which the metabolic pathways of cardiovascular diseases and viral infectious diseases:Viral were reduced.The results of in vitro fermentation test showed that the barley?-glucan had good fermentability.After 24 h,the pH of the blank group decreased from 7.04 to 6.48,and the pH of the barley?-glucan group decreased to 4.51.Compared with the blank group,the content of SCFAs in the fermentation broth after fermentation for 24 h in vitro was:butyric acid>propionic acid>acetic acid,which were 2.53 times,1.53 times and 1.21 of the blank group,respectively. |
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