Ileal effluent as a fermentation substrate: implications for butyrate production in the colon

Fermentation of fiber can lead to an enhanced production of short chain fatty acids (SCFA) and, hence, contribute to the proposed anticarcinogenic properties of butyrate in the colon. The fermentation of fiber isolates and the corresponding ileal effluents has been compared under in vitro conditions. Yield of SCFA per gram of substrate fermented was similar for isolates and fiber-enriched effluents (~4.9 mmol/g) and it could be inferred that nonfiber components of effluent alsogenerated SCFA. Butyrate production was highest for glucan-based polymers (~30% total SCFA) and, from the measured acidogenic profile, production of SOFA will occur mainly in the proximal colon. The buffering capacity of ileal effluents during fermentation restrict the potential for a reduction in pH during acidogenesis compared to fiber isolates. This buffering capacity could limit the bioavailability of butyrate in the colon and, hence, the ability to satisfy the proposed antineoplastic properties of butyrate in the colon. [ABSTRACT FROM AUTHOR]