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Appl. Environ. Microbiol., May 1996, 1589-1592, Vol 62, No. 5
TL Miller and MJ Wolin
The pathways of short-chain fatty acid (SCFA; acetate, propionate, and
butyrate) formation from glucose were determined for the human fecal
microbial communities of two subjects. The pathways were identified by
radioisotope analysis of the SCFA and CO2 obtained after incubation of
fecal suspensions with glucose under 20% CO2 with [1-14C]glucose, [3,4-
14C]glucose, or 14CO2. Acetate was chemically degraded to learn the
labeling of the methyl and carboxyl carbons. The labeling of CO2 and
acetate showed that the major route of glucose catabolism was the
Embden-Meyerhof-Parnas pathway, with production of CO2 from pyruvate
carboxyl carbon. Labeling of the methyl and carboxyl carbons of acetate by
14CO2 or [3,4-14C]glucose proved that acetate was formed from CO2 by the
Wood-Ljungdahl pathway. CO2 reduction accounted for about one-third of the
acetate formed by suspensions from subject 1 and about one- fourth of the
acetate formed by suspensions from subject 2. Propionate was formed by a
CO2 fixation pathway, and butyrate was formed by classical routes of
acetyl-S coenzyme A condensation. The amount of CO2 formed from [1-14C]
glucose and acetate labeling patterns obtained with the other 14C
precursors indicated that the Entner-Doudoroff,
transketolase-transaldolase, and heterolactic pathways were not
significant. Fermentation of cabbage cellulose by subject 1 followed the
same pathways as were used for glucose. The results with suspensions from
subject 2 suggested that some radioactive acetate was formed from the C-3
of glucose by the Bifidobacterium pathway.
Copyright © 1996, American Society for Microbiology
Pathways of acetate, propionate, and butyrate formation by the human fecal microbial flora
Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509, USA. terry.miller@wadsworth.org
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