The effect of the undigested fraction of maize products on the activity and composition of the microbiota determined in a dynamic in vitro model of the human proximal large intestine.

To investigate the effect of 5 newly developed maize-based fibers on the activity and composition of the microbiota in the colon. The fibers tested were glucose-based and had variable structures, including 2 resistant starch preparations, soluble corn fiber, pullulan, and soluble fiber dextrin. The fibers were predigested, mono- and disaccharides were removed, and the residual polymer was used to assess the production of microbial metabolites and changes in composition of the microbiota using a dynamic, validated, in vitro model of the large intestine. Microbial metabolite analysis showed an increase in short-chain fatty acids for all fibers, with varying levels of butyrate production for each fiber. The greatest increase of butyrate, both in terms of absolute amounts and as a proportion of total short-chain fatty acids, was observed for pullulan. All fibers also reduced toxic metabolites from protein fermentation compared to the poorly fermentable control (cellulose). Microbial composition was assessed using a micro-array platform. All fibers showed increases of bifidobacteria and some Lactobacillus species, although different species were stimulated by different fibers. Pullulan showed the largest increase of bifidobacteria. All fibers showed prebiotic activity in terms of increases in growth and/or activity of beneficial microbes. In addition, compared to the control, health-promoting metabolites were produced in higher amounts, while putrefactive metabolites were reduced for all fibers. The importance of the findings lies in the fact that the newly developed, maize-based fibers shift the intestinal environment to a healthier milieu, with increased health-promoting metabolites and health-beneficial microbes.