MUCIN SECRETION IN GERM-FREE RATS FED FIBER-FREE AND PSYLLIUM DIETS AND BACTERIAL MASS AND CARBOHYDRATE FERMENTATION AFTER COLONIZATION

The effect of psyllium on mucin secretion was determined by comparing water-soluble and -insoluble fractions of excreta from germfree rats f ed a fiber-free (FF) diet or a diet containing psyllium seed husk (PS) . Excreta from the same rats after colonization with a rat mixed cecal culture were separated into water-soluble, plant, and bacterial fract ions to compare the remaining carbohydrate and the mass of bacteria. T he sugar composition and water solubility of carbohydrate in excreta f rom germfree rats fed FF diets indicated that a primary fermentable su bstrate was mucin. PS increased fecal excretion of mucin-derived sugar s almost threefold in germfree rats. Fecal carbohydrate was reduced fr om 619 to 237 mumol/g of dry feces and mostly in the bacterial fractio n when rats fed an FF diet were colonized. The total sugar content and the amount of muramic acid, but not bacterial counts and mass, indica ted that PS increased fecal bacteria. Fractionation of excreta from PS -fed rats was complicated by a gel which, based on sugar composition, was PS. Sugar composition of the water-soluble fraction from excreta f rom PS-fed rats suggested that it contained some bacterial component, possibly exopolysaccharides and some of the PS, but not mucin. PS dige stibility ranged from 60 to 80%, depending on what fecal fraction was used for output. Because of the presence of PS-derived sugars in the g el and soluble fraction, it was not possible to determine which, if an y, of the PS digestibilities was correct.