Production of Short-Chain Fatty Acids (SCFA) During in vitro Fermentation of Fibers

Abstract

Increasing dietary fiber has been shown to improve colonic health and reduce the risk of colon cancer. One aspect of fiber consumption is its fermentation by colonic microflora to produce short-chain fatty acids (SCFA). The major SFCA produced are acetic, propionic and butyric acids. Butyric acid is absorbed by the colonic mucosa as its major energy source. The concentration of SCFA in the feces can be measured and the results extrapolated to production in the colon. However, this is probably not a true reflection of SCFA production since SCFA are absorbed and utilized by the colon epithelial cells. In our study, fresh fecal samples were mixed with 9 different fibers with glucose serving as the control, incubated at 37°C for 24h. SCFA production was measured at 0,4,8,12, and 24h. This approach avoids loss of SCFA by absorption into the body. SCFA production after 24h was 42.35 ± 5.5mg/ml for 8 of the 10 samples. Unifiber™ had a lower production of total SCFA (33.5mg/ml) after 24h and Benefiber™ had a high production of SCFA (54.6mg/ml). To allow for differences in total SCFA production, the percentage of total SCFA was calculated for three major fatty acids. Percent averages after 24h were: Acetic acid 44.9% ± 12.9. with the highest production from glucose and the lowest from cellulose, 69.2% and 17.7%, respectively. Propionic acid 32.5% ± 10.4, with the highest from cellulose and the lowest from glucose, 55% and 20.2%, respectively. Butyric acid 22.3% ± 9.0, with the highest from Metamucil™ and the lowest from cellulose, 38.5% and 9.0%, respectively. There was no consistent pattern as to when the SCFA are formed over the 24h period. Thus, in vitro fermentation of different fibers ail yield SCFA, but the concentrations of the various SCFAs vary among the fibers.