Fibers with different solubility characteristics alter similarly the metabolic activity of intestinal microbiota in rats fed cereal brans and inulin

We compared the effects of different sources of fiber (rye-bran, oat-bran, wheat-bran) and inulin on the activity of fecal bacterial enzymes and concentration of short chain fatty acids (SCFA) in the colonic contents of rats. A diet without fiber was used as a control. The cereal brans and inulin had similar, increasing effect on the activities of beta-glucuronidase and urease (P < 0.05). All bran diets also increased beta-glucosidase activity while the increase by inulin was non-significant. Concentration of total SCFA was higher in the inulin and rye-bran groups compared to non-fiber and wheat-bran groups (P < 0.05). Concentration of butyrate was higher in rye-bran and inulin groups compared to the non-fiber group (P < 0.05), and that of propionate higher in the inulin group compared to non-fiber and wheat-bran groups (P < 0.05). The SCFA profile in the oat-bran group did not differ significantly from SCFA profile in the other groups. These findings indicate that the source of the fiber does not markedly affect the enzyme activities of the fecal bacterial microbiota, but may cause differences in the profile of SCFA in the rat colon.