In Vitro Fermentation Of Six Different Microwave-synthesized Polydextrose With Different Molecular Weight And Their Impact On The Composition And Metabolites Of Human Gut Microbiota

Due to its monosaccharide linkage,Polydextrose cannot be hydrolyzed by the body's own digestive enzymes,can "pass" the upper digestive tract of the body,reach the colon,be slowly fermented by intestinal microbes,metabolize to produce short-chain fatty acids,and regulate intestinal bacteria.It also has physiological functions such as controlling appetite and regulating energy metabolism but,the molecular weight effects of polydextrose segments to regulate the intestinal microecology,has not been reported much in the literature.The purpose of this study was to investigate the effects of different molecular weight fractions of Polydextrose on regulation of human intestinal flora and production of fermentable metabolites(SCFA's).Six-microwave synthesized Polydextrose(PDX)with different molecular weight and a resistance starch(RS)as a control sample were inoculated with the slurry of human feces from health volunteers and fermented using pH-controlled batch system as the fermentation model.By controlling and maintaining the pH and temperature values of the fermentation system,the human colon was simulated and the colonic peristalsis rate was determined by using starch as a control group and in vitro anaerobic fermentation experiments on polydextrose of different molecular weight fractions.The fermentation broth flora and its metabolites were studied by 16s rRNA sequencing and chromatographic methods.The effects of polydextrose with different molecular weight fractions on the structure,biodiversity,and key metabolites of short-chain fatty acids were analyzed.The results showed that,all six PDX segments types that were fermented expresses great difference in both metabolic production and the microbial community composition which shows that the change of molecular weight has a significant effect on microbial metabolism.In particular,PDX2 fermentation increase the relative abundance of Actinobacteria especially members of genus Bifidobacterium and lowered the level of firmicutes.Moreover,it dramatically modified the gut microbial species at family level by increasing the level of Streptococcaceae,Bifidobacteriaceae and Lactobacillaceae which are responsible for strong immune defense and host's wellbeing and decreased the gut microbiota that have be described to completely relate with obesity,such as Ruminococcaceae,Coriobacteriaceae and Lachnospiraceae.Conclusion:The six molecular weight fractions of polydextrose can be metabolized by human intestinal microbes,producing a large number of short-chain fatty acids,which have the ability to regulate the composition of human intestinal flora,promote the proliferation of beneficial bacteria and inhibit the growth of harmful bacteria and hence showed good prebiotic activity.