Effect of pH on Oligosaccharide Fermentation by Porcine Cecal Digesta

Abstract

Lactate and succinate sometimes accumulate in the cecum and colon of monogastric animals, often resulting in disturbed gut function. The present study assessed the critical point of digesta pH at which lactate and succinate begins to accumulate during fermentation of oligosaccharides under the pig cecal in vitro conditions. Xylosylfructoside, isomaltooligo-saccharides and raffinose were incubated with pig cecal digesta dissolved in one of seven buffers with different pHs (4.0, 4.5, 5.6, 5.8, 6.0, 7.0 and 7.5). Lactate, acetate, propionate and butyrate were predominantly produced. The production of acids was significantly affected by initial pH of culture, oligosaccharides and two-way interaction effect between sugar and pH except for formate. Lactate accumulated under conditions of initial low pH. The critical initial pH that induced lactic acid fermentation depended on the type of oligosaccharides; 5.0 for isomaltooligosaccharides and 6.0 for raffinose and xylosylfructoside at 6h incubation. Lactate molar ratio decreased along with incubation except for xylosylfructoside. Induction of lactic acid fermentation in large intestine can be avoided if digesta pH is maintained at least above 6.0 when oligosaccharides are fed to the pig.