Structural Differences among Alkali-Soluble Arabinoxylans from Maize (Zea mays), Rice (Oryza sativa), and Wheat (Triticum aestivum) Brans Influence Human Fecal Fermentation Profiles

Human fecal fermentation profiles of maize, rice, and wheat bran and their dietary fiber fractions released by alkaline-hydrogen peroxide treatment (principally arabinoxylan) were obtained with the aim of identifying and characterizing fractions associated with high production of short chain fatty acids and a linear fermentation profile for possible application as a slowly fermentable dietary fiber. The alkali-soluble fraction from maize bran resulted in the highest short chain fatty acid production among all samples tested, and was linear over the 24 h fermentation period. Size-exclusion chromatography and H-1 NMR suggested that higher molecular weight and uniquely substituted arabinose side chains may contribute to these properties. Monosaccharide disappearance data suggest that maize and rice bran arabinoxylans are fermented by a debranching mechanism, while wheat bran arabinoxylans likely contain large unsubstituted xylose regions that are fermented preferentially, followed by poor fermentation of the remaining, highly branched oligosaccharides.