Preparation Of Oat Polysaccharides And Its Oligosaccharides And Their Effects On Intestinal Microorganisms

Oats polysaccharides mainly contain?-glucan,which is abundant in oats bran.?-glucan is a common soluble dietary fiber.The hydrolysate of?-glucan,?-gluco-oligosaccharides,is also considered to be functional substances with potential prebiotic properties.In recent years,there has been an increasing number of studies on the probiotic function of?-glucan at home and abroad,but there is little research on the effect of plant-derived?-gluco-oligosaccharides on intestinal flora currently.And the reports about the intestinal flora's fermentation characteristic differences with?-glucan and its hydrolysate?-gluco-oligosaccharides as carbon source are rarer.In addition,the development of new prebiotics is mainly through in vitro static fermentation and animal experiments such as mice.A new type of gastrointestinal reactor has been developed in this laboratory.It has been verified that it can accurately simulate the dynamic characteristics of the large intestine such as peristalsis,emptying and mixing.It can regulate the pH online,and can achieve sterile and anaerobic culture.Based on this,in this study,oats?-glucans(OGs)were extracted and purified from oat bran,and Oats?-gluco-oligosaccharides(OGOs)were prepared by acid hydrolysis of OGs.By adding OGs and OGOs as carbon source of the culture medium respectively,this study performed in vitro anaerobic fermentation of fecal flora in the anaerobic tube and gastrointestinal reactor to study the effects of OGs and OGOs on the structure and metabolism of intestinal flora,and to explore the fermentation characteristic difference of intestinal flora with OGs and OGOs as carbon source.The main contents and results are as follows:(1)Preparation of oat?-glucans(OGs)and their oligosaccharides(OGOs).Firstly,OGs were extracted and purified from oat bran by hot water extraction.Then OGOs were prepared by acid hydrolysis of OGs.By determinating the composition of OGs and OGOs prepared in different batches,the purity of OGs is(89.71±3.69)%,and the purity of OGOs can reach more than 90%,both of which meet the requirements of subsequent fermentation experiments.Finally,the molecular mass of OGs and the degree of polymerization of OGOs were determined by gel permeation chromatography and time-of-flight mass spectrometry,respectively.The molecular weight of OGs was 1.34×10~5 Da;and the degree of polymerization of OGOs was 2?11.(2)In vitro simulation of the digestion of OGs and OGOs in human saliva,gastric juice and intestinal fluid.The results showed that the total carbonhydrate and reducing sugar contents of OGs and OGOs samples were basically unchanged after digestion of saliva and gastrointestinal fluids.The molecular weight of OGs did not decrease with the digestion process.And the distribution of polymerization degree of OGOs also did not change.It shows that OGs and OGOs will not be digested by the body itself,and can smoothly pass through the digestive system and reach the large intestine"safely".(3)Through in vitro static fermentation of fecal flora from healthy people and type 2diabetic patients,the effects of OGs and OGOs on the structure and metabolism of intestinal flora from different sources were studied.The results showed that OGs and OGOs can significantly promote the growth of beneficial bacteria in the intestinal flora and the production of short-chain fatty acids(SCFAs).Among them,using OGs as carbon source can significantly promote butyric acid production of healthy people and type 2 diabetes intestinal flora.And OGOs as a carbon source is more conducive to promoting the production of acetic acid and propionic acid in the intestinal flora of type 2 diabetes.At the same time,the results of in vitro fermentation of fecal flora in healthy and type 2 diabetic individuals using OGs and OGOs as carbon sources further verified the reliability of the above fermentation results,indicating that the effects of OGs and OGOs on intestinal flora are stable among individuals.(4)The fermentation of OGs and OGOs in the large intestine was simulated in vitro in a gastrointestinal reactor dynamic model.By monitoring the real-time pH value of the fermentation broth and the amount of NaOH solution supplement,it was judged that the gastrointestinal tract reactor can simulate the pH regulation in the large intestine during the fermentation process,and maintain the fermentation process stable.By measuring the content of total carbohydrate,reducing sugar and SCFAs in the fermentation broth every 12 hours,it was found that after adding OGs and OGOs for fermentation,the carbohydrate metabolism level of intestinal flora increased,and the production of SCFAs increased significantly.