title: Taurocholic acid adsorption during non-starch polysaccharide fermentation: an in vitro study.
abstract: The association of radiolabelled taurocholic acid with the solid fraction of a faecal fermentation mixture was measured. A human faecal inoculum was incubated with [24-14C]taurocholic acid and several non-starch polysaccharide sources (pectin, wheat bran, ispaghula (Plantago ovata) husk and seed), glucose or a substrate-free control. Portions of fermentation mixture were taken at 0, 3, 6, 21 and 24 h and centrifuged to acquire a supernatant fraction and a pellet containing the fermentation residue. 14C was measured in supernatant fractions and pellets at all time points. Volatile fatty acids (VFA) were measured at 0 and 24 h to confirm bacterial growth. Radioactivity in the pellet increased over time for all substrates. Glucose resulted in the greatest incorporation of taurocholic acid into the pellet, followed by pectin. At 24 h the proportion of the total radioactivity found in the pellet was 92% for glucose, 79% for pectin, 60% for wheat bran, 59% for ispaghula seed, 53% for ispaghula husk and 26% for the control (mean of duplicates). Glucose and pectin produced the greatest quantity of VFA at 24 h. VFA production was highly correlated with radioactivity in the pellet (r0.976, P < 0.005). These results suggest that the bile acid binding capacity of a faecal culture mixture may be strongly influenced by the fermentability of the available substrate and hence related to bacterial metabolic activity.
authors.affiliation: Gastro-Intestinal Laboratory, Western General Hospital, Edinburgh.
authors.forename: I C
authors.initials: IC
authors.lastname: Gelissen
authors.forename: M A
authors.initials: MA
authors.lastname: Eastwood
mesh_terms: D000327:Adsorption; D001419:Bacteria / Q000378:metabolism; D002250:Carbon Radioisotopes; D004040:Dietary Carbohydrates / Q000378:metabolism*; D005232:Fatty Acids, Volatile / Q000096:biosynthesis; D005243:Feces / Q000737:chemistry / Q000382:microbiology*; D005260:Female; D005285:Fermentation / Q000502:physiology*; D006801:Humans; D011134:Polysaccharides / Q000378:metabolism*; D013656:Taurocholic Acid / Q000493:pharmacokinetics*
chemical_list: D002250:Carbon Radioisotopes; D004040:Dietary Carbohydrates; D005232:Fatty Acids, Volatile; D011134:Polysaccharides; D013656:Taurocholic Acid