Effect Of Resistant Starch On Intestine Flora In Rats And The Mechanism Of Action

Resistant Starch (Resistant Starch, RS) can’t be digested in the small intestine, but can be used by the intestinal flora for fermentation.RS has many similar physiological functions of dietary fiber,which has good processing characteristics, at the same time can be widely added to all kinds of food.At present domestic research about the effects of RS on the intestinal flora are very few, the foreign research of RS in this field mainly through the way of collecting feces or in vitro fermentation, the effects and the potential mechanism of RS on flora in animal colon is still lacking of large amounts of datas.This topic chose the adult KM rats as experimental animals, respectively fed the basal diet and the diet which adding different content of high amylose maize RS.Free water and food in rats access during the tests for4weeks of the trial period, the research focuses on the change of flora and short chain fatty acids in the ascending colon, transverse colon and descending colon and their inner relation;Simulated intestinal anaerobic environment at the same time, build an effective system of in vitro fermentation by detecting the change of flora and short chain fatty acids;Added four kinds of exogenous flora in the resistant starch fermentation system, it research the effect of exogenous flora on RS,and the mechanism of RS on adjusting the flora.The main results were as follows:1. Animal experiments:(1) RS can reduce pH in the ascending colon, transverse colon and descending colon effectively,high content of RS showed great advantage in reducing pH,specially in the descending colon, but needed more time to build a stable acidic environment.(2) RS can increase the short chain fatty acids as acetic acid, propionic acid, butyric acid effectively, and high content of RS is better than low content of RS, in the descending colon especially.Acetic acid is mainly produced in the ascending colon;Propionic acid is mainly produced in the descending colon.Butyric acid is mainly produced in the transverse colon.(3) RS can obviously promote the proliferation of lactobacillus and bifidobacterium, inhibit the growth of escherichia coli and enterococcus, and high content of RS effect more apparently,especially in the descending colon.Lactic acid bacteria are mainly distributed in the ascending colon;Bifidobacteria are mainly distributed in the transverse colon and descending colon;E. coli and enterococcus evenly distributed in all the segments of the colon.(4) RS can increase the diversity of the intestinal flora, but adding high content of RS may cause acidic environment too low, inhibit the growth of some normal flora.2. In vitro fermentation experiments:(1) based on the different content of RS in vitro fermentation experiments, the results showed that the RS in vitro fermentation results consistent with the changes of in fermentation,so the in vitro fermentation system is effective.(2) The results showed that RS regulate the growth of Lactobacillus acidophilus by as a carbon source; RS regulate the growth of Bifidobacterium and Escherichia coli by acidic environment; RS regulate the growth of fecal bacteria by improving the competition of the flora. It shows that the mechanisms of rugulation on flora by RS are different. From these results we can get the following conclusions:(1) RS can promote the growth of lactic acid bacteria, especially in ascending colon, because it can provide sufficient carbon, the most lactic acid bacteria distribute in the ascending colon and produce a large amount of acetic acid.(2) RS promote the growth of bifidobacteria by lowering the pH of the intestine, since the bifidobacteria are anaerobic bacteria, most located in transverse and descending colon, and therefore high levels of RS has more advantages in generating more propionate and butyrate.(3) RS is also suppressed the growth of E.Coli by lowering the pH, E. coli uniform distributed in the colon, which excess will inhibit the acid of RS.(4) RS suppressed the growth of Enterococcus by promoting the growth of probiotics and enhancing the competitive. Enterococcus distributed in the colon uniformly, that can produce propionic acid and butyric acid, but it has a small number,that does not affect the acid of RS.(5) RS can increase the diversity of the intestinal flora, but adding high levels of RS get the opposite effect.