Shifts in Bacterial Community Compositions during i n v itro Fermentation of Amylopectin and Resistant Starch by Colonic Inocula of Pigs

Abstract

Starch, which escapes the digestion of the small intestine in humans and animals, may serve as a carbon source for bacterial fermentation in the hindgut. This study aimed to compare the fermentation characteristics of amylopectin and resistant starch by the colonic microbiota of pigs, and also to reveal the shifts in bacterial community compositions during the fermentation. Two types of resistant starch (RS2 and RS4) and amylopectin were used as substances in an in vitro fermentation test. As compared with resistant starch, amylopectin was more fermentable by colonic microbiota, while RS4 used in this study showed very poor fermentation characteristics. Fermentation of amylopectin produced more short-chain fatty acids with a higher propionate proportion and a lower butyrate proportion. Lactate was produced in the early period of amylopectin and RS2 fermentation but consumed entirely at the end of fermentation. Pyrosequencing analysis showed that the abundance of Firmicutes decreased significantly along with the increase of Bacteroidetes during the fermentation of amylopectin and RS2. In particular, Bacteroides spp. (such as B acteroides vulgatus and B. uniformis) became predominant in the bacterial community. These results suggest that Bacteroides spp. may play important roles in the degradation of starch in the pig hindgut.