Investigation Of The Effects Of MACs On Human Intestinal Microbiota By Vitro Gut Model

Human digestive tract colonizes trillions of bacterial cells and food components determine human gut microbiota assemblage.Probiotics are believed to promote the growth of beneficial bacteria in the intestinal tract and produce metabolic products beneficial to the host.Therefore,probiotics are widely used to improve intestinal function.It has long been known dietary habits associate with the human microbiota enterotypes;however the factors that determine the enterotypes remain unclear.There was a correlation between the structure of intestinal microbiota and age,and it was believed that the intestinal microbiota of the host began to degrade after the age of 70,with reduction of the beneficial bacteria and the increase of pathogenic bacteria.The changes of intestinal microflora in the elderly have always been concerned by people,because the change in the population of microbiota are closely related to a variety of intestinal diseases.Firstly,batch fermentation was used to carry out in vitro fermentation experiments on feces of people of different ages.16 s RNA sequencing was used to sequence fecal microbiota and fermentation culture products.Meanwhile,the content of short-chain fatty acids,degradation rate of substrates,gas production and other metabolic indexes in fermentation broth were detected by gas chromatography and TLC.Nonparametric test and redundancy analysis(RDA)was also performed to analyze the differences of the data.we choosed lactulose(LAU),raffinose(RAF),fructo-oligosaccharide(FOS),galactooligosaccharide(GOS),Isomaltooligosaccharide(IMO),mannitol(MAI),xylitol(XYI),manno-oligosaccharide(MOS),xylooligosaccharide(XOS),inulin(INU)and starch(STA)as the carbon sources in the medium.Bacterial composition after fermentation were measured using 16 s rRNA sequencing and SCFA were analyzed by gas chromotograghy.The results showed that the microbiota community structure of feces is very similar between young aged group(20-40 years)and middle group(40-60 years old),and only the bacteroides content in the intestinal flora of the middle group was significantly higher than that in the young-aged group.The results of 16 s rRNA sequencing showed that in the inulin group,the pathogenic bacteria in the middle group increased obviously.In contrast,the beneficial bacteria in the young-aged group were obviously enriched.For the second experiment,microbiota structures after in vitro batch fermentation of FOS,GOS,IMO,lactulose,raffinose,starch and XOS are clustered together by fifteen fecal microbiota,while the bacterial structures of inulin,mannitol and MOS were grouped together,separated to xylitol and control medium(YCFA).Isomaltooligosaccharides(IMO)coupled with the faster dilution rates and lower pH were parameters required to sustain the growth of Prevotella copri in the chemostat based on metagenomic sequencing.Amylo-?-1,6-glucosidase,pectin and xylan lysases were the carboxylates hydrolase enzymes associated with Prevotella enterotypes.In conclution,current results showed that even people who are very close in age had similar intestinal bacteria groups in feces,the effects of diet on the metabolism and community structure of the two groups were different between the very closed age.In addition,difference in the fecal microbiota enterotypes shows different metabolic profiles on the utilization ofprobiotics.The key nutritional factor and fermentative parameters identified by in vitro batch and chemostat systems will help us to understand the nutritional requirements for the formation of enterotypes.