FERMENTATION OF VARIOUS DIETARY FIBER SOURCES BY HUMAN FECAL BACTERIA

Eleven fiber-rich substrates were subjected to in vitro incubation wit h fecal bacteria from each of three adult male volunteers to assess su bstrate organic matter disappearance (OMD), short-chain fatty acid (SC FA) production, and the potential water holding capacity (PWHC) of fer mented residues. Substrate OMD ranged from 83.3% (citrus pectin) to 5. 8% (oat fiber). Total SCFA production (mmol/g substrate OM) was highly correlated to OMD and ranged from 9.64 (gum arabic) to 0.48 (oat fibe r). Molar ratios of acetate:propionate produced during fermentation va ried considerably among substrates, ranging from 1.5 for guar gum to 1 2.6 for citrus pectin. PWHC, an estimate of potential fecal bulking ef fects, was negatively related to OMD (r = -0.88) and ranged from 4.47 (oat fiber) to 0.71 (citrus pectin) g H2O/g substrate dry matter. In v itro fermentation techniques call be potentially useful predictors of in vivo responses to dietary fiber sources.