Content area
Full Text
(ProQuest: ... denotes non-US-ASCII text omitted.)
[dagger]
Current address: International Livestock Research Institute, PO Box 5689, Addis Ababa, Ethiopia.
The microbial community resident in the human colon is a highly complex consortium of many different bacterial species. The application of molecular tools targeting the 16S rRNA gene has revealed that the numerically dominant groups are low G+C % Gram-positive bacteria and Gram-negative Bacteroidetes; however, many phylotypes remain uncultured and consequently poorly characterised(1). The microbiota plays an important role in host health through various mechanisms, such as protection against pathogenic bacteria and provision of nutrients, and its composition can be modulated by dietary means, which can lead to either more health-promoting or more detrimental consequences for the host(1). One way of modulating the gut microbiota is through the consumption of prebiotics, non-digestible food ingredients that pass through the upper gut and are selectively fermented by colonic bacteria. This leads to specific changes in the composition and/or activity of the gut microbiota that confers benefits upon host well-being and health(2,3). The dietary fructan inulin and its breakdown product fructo-oligosaccharide are particularly well-studied prebiotics, and evidence supporting their health-promoting effects, mostly in animal models, is accumulating rapidly(3,4). A direct consequence of inulin ingestion is stimulation of lactic acid bacteria (lactobacilli and bifidobacteria) within the gut microbiota(2). While the bifidogenic effect of inulin is well demonstrated, it is less clear whether this is a characteristic of the whole genus, or whether certain Bifidobacterium spp. are selectively stimulated. Several Bifidobacterium spp. are commonly found in the adult human colon(5-8). The degradation of fructo-oligosaccharides seems to be widespread among bifidobacterial strains in pure culture, while fewer strains are able to utilise inulin(9). In vivo, however, cross-feeding of fructo-oligosaccharides and fructose from primary inulin degraders might lead to a stimulation of other bifidobacteria(9).
Possible effects of inulin on other members of the gut microbiota are less well studied; however, it is increasingly recognised that prebiotics are likely to lead to further microbial changes other than bifidogenesis(10). For example,...