Physicochemical Properties Of Highland Barley β-glucan And Its Effects On Intestinal Flora

Highland barely 25 is a Tibetan alfalfa variety with highβ-glucan bred in 2002,and itsβ-glucan content can reach 8.62%.β-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 ofβ-glucan.No related research has been found on the physicochemical properties of Highland barely 25β-glucan,and its influence on the intestinal flora has yet to be discovered.In this experiment,the preparation of theβ-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 ofβ-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 ofβ-glucan were studied by in vitro fecal fermentation and 16S rDNA high-throughput sequencing.The effect of in vitro fermentation ofβ-glucan on microbial metabolites was studied by gas chromatography.The research results are as follows:（1）The purity of crudeβ-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 bariumβ-glucan showed that the barleyβ-glucan was mainly composed of glucose.And glucose constitutes a sugar chain byβ-1,3-Glup andβ-1,4-Glup linkage.The greenβ-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 ofβ-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 barelyβ-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 barleyβ-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 barleyβ-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.