The Colonic Microbes in Fermentation andPhysiology Seiko HOSHI and Takaji YAJIMA Department of Nutritional Research, NutritionScience Institute,
Meiji Milk Products Co., Ltd. Colonic bacteria ferment nutrients escapeddigestion and absorption in the small intestine to get energy fortheir proliferation, and result in luminal accumulation of theirfermentation products. Colonic fermentation and their products areinfluenced by available substrates which vary chemical compositionsand physical states. Plant fibers, resistant starch, nondigestibleoligosaccharides and resistant proteins are principal substratesfor colonic bacteria, and are anaerobically metabolized to variousorganic acids, mainly short-chain fatty acids (acetate, propionateand butyrate), ammonia and amines. Short-chain fatty acids arerapidly absorbed across colonic mucosa and used as an energynutrient. Short-chain fatty acids, besides their energy supplier,play a role as luminal chemical stimuli that can modify epithelialproliferation, intestinal blood flow, motility and secretion. Theeffects vary among short-chain fatty acids, and are dose-dependent.The sensory mechanism, therefore, of the gastrointestinal tractsmust be able to detect not only the presence of individualshort-chain fatty acids, but also their concentration.
Key words: colonic bacteria, nondigestible carbohydrates,short-chain fatty acids, gut function |
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