NEUTRAL-SUGAR DETERMINATION BY HPAEC-PAD TO CHARACTERIZE POLYSACCHARIDE DEGRADATION BY COLONIC BACTERIA

In vitro methods are widely used to characterise dietary fibre ferment ability in the human hind gut. The activity of faecal bacteria can be followed by measuring fermentation products and substrate degradation. This paper describes a method for establishing neutral-sugar profiles by HPAEC-PAD during in vitro fermentation studies. Freeze-dried ferme ntation residues are hydrolysed with H2SO4, and the monomers are separ ated on an anion-exchange column using a reverse NaOH gradient. Sulpha te ions are removed from hydrolysates on-line with a special ion-excha nge guard column. 2-D-deoxyribose is used as internal standard for qua ntification. A method for separating all neutral sugars that typically occur in dietary fibre is given. Possibilities for enhancing the reso lution for other purposes are suggested. Compared to GC the described method is particularly attractive for routine analyses. Data relating to the decreasing levels of neutral sugars in fermentation residues of oat bran fractions that differ in their mixed-linked beta-glucan cont ent are given and degradation patterns of the polysaccharides present in these substrates are discussed.