Low amounts of dietary fibre increase in vitro production of short-chain fatty acids without changing human colonic microbiota structure

Daisuke Sasaki,Takahiro Yasuda,Naoko Ikuta,Ro Osawa,Itsuko Fukuda,Kengo Sasaki,Akihiko Kondo

doi:10.1038/s41598-017-18877-8

Abstract

This study investigated the effect of various prebiotics (indigestible dextrin, α-cyclodextrin, and dextran) on human colonic microbiota at a dosage corresponding to a daily intake of 6 g of prebiotics per person (0.2% of dietary intake). We used an in vitro human colonic microbiota model based on batch fermentation starting from a faecal inoculum. Bacterial 16S rRNA gene sequence analysis showed that addition of 0.2% prebiotics did not change the diversity and composition of colonic microbiota. This finding coincided with results from a clinical study showing that the microbiota composition of human faecal samples remained unchanged following administration of 6 g of prebiotics over seven days. However, compared to absence of prebiotics, their addition reduced the pH and increased the generation of acetate and propionate in the in vitro system. Thus, even at such relatively low amounts, prebiotics appear capable of activating the metabolism of colonic microbiota.

Highlights

Prebiotics are defined as “a selectively fermented ingredient that results in specific changes in the composition and/or activity of the gastrointestinal microbiota, conferring benefit(s) upon host health”[1]
The aim of the present study was to investigate the impact of a low dosage (0.2%) of prebiotics (DEX, αCD, or DXR) on human colonic microbial ecology and metabolic end-products using an in vitro batch fermentation system, KUHIMM
Bacteria belonging to the genus Bifidobacterium, which were abundant in the phylum Actinobacteria in our system, are known to produce acetate[36,37]

Summary

Introduction

Prebiotics are defined as “a selectively fermented ingredient that results in specific changes in the composition and/or activity of the gastrointestinal microbiota, conferring benefit(s) upon host health”[1]. By carefully constructing the necessary anaerobic conditions, we previously developed an in vitro batch fermentation system (hereafter referred to as Kobe University Human Intestinal Microbiota Model, KUHIMM) that is capable of hosting more than 500 microbial species found in a human faecal inoculum and can effectively mimic human colonic microbiota[13]. The aim of this study was to assess the effect of relatively low amounts of three different prebiotics, i.e., indigestible dextrin (DEX), α-cyclodextrin (αCD), and dextran (DXR), on human colonic microbiota using our KUHIMM system (Table 1). We compared pH changes and production of SCFAs. In addition, a small human trial was performed with a daily intake of 6 g of DEX or αCD to compare the microbiota composition in actual human faeces with that in the KUHIMM

Objectives

Methods

Results

Conclusion