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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Cell Wall Biology and Utilization Research » Research » Publications at this Location » Publication #285880

Title: In vitro degradation and fermentation of three dietary fiber sources by human colonic bacteria

item BLISS, DONNA - University Of Minnesota
item Weimer, Paul
item Jung, Hans Joachim
item SAVIK, KAY - University Of Minnesota

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2013
Publication Date: 5/15/2013
Citation: Bliss, D.Z., Weimer, P.J., Jung, H.G., Savik, K. 2013. In vitro degradation and fermentation of three dietary fiber sources by human colonic bacteria. Journal of Agricultural and Food Chemistry. 61:4614-4621.

Interpretive Summary: The bacterial fermentation of soluble plant fibers by anaerobic bacteria is important in human and animal digestion, and in the bioconversion of plant material to fuels and chemicals. However, the ability of bacteria from the human colon to degrade soluble fiber is largely unexplored. We measured production of short-chain fatty acids and gases produced from three plant fiber preparations by human colonic bacteria in feces. The feces from unadapted donors fermented all three fiber sources to varying degrees, and produced different amounts of fermentation products. Fecal inocula from donor subjects adapted to these dietary fibers displayed similar fermentation characteristics to the unadapted inocula, suggesting that the community is stable and well-adapted with respect to these fiber sources. The results provide baseline data for evaluating the ability of colonic bacteria to enzymatically degrade complex plant fibers.

Technical Abstract: Although clinical benefits of dietary fiber supplementation seem to depend in part on the extent of fiber degradation and fermentation by colonic bacteria, little is known about the effect of the type of supplemented fiber on bacterial metabolism. In an experiment using a non-adapted human bacterial population from three normal subjects, in vitro fermentation of guar gum (GA) was greater than that of psyllium fiber (PSY), which was greater than that of carboxymethylcellulose (CMC). In a separate experiment, in vitro fermentation of feces of 52 subjects with fecal incontinence before and after random assignment to and consumption of one of the three fiber supplements or placebo for 20-21 days showed that the fiber consumed did not increase its degradation by fecal bacteria. Findings suggest that increased intake of a fiber source by humans is not expected to result in bacterial adaptation that would require continually larger and eventually intolerable amounts of fiber.