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Por favor, use este identificador para citar o enlazar a este item: http://hdl.handle.net/10261/11960

Impact of pH on Lactate Formation and Utilization by Human Fecal Microbial Communities

AutorBelenguer, Álvaro ; Duncan, Sylvia H.; Holtrop, Grietje; Anderson, Susan E.; Lobley, Gerald E.; Flint, Harry J.
Palabras claveButyrate-producing bacteria
Targeted oligonucleotide probes
Continuous culture system
In-situ hybridization
Human feces
Human gut
Human colon
Fermentation products
Fecha de publicación2007
EditorAmerican Society for Microbiology
CitaciónApplied and Environmental Microbiology 73(20): 6526-6533 (2007)
ResumenThe human intestine harbors both lactate-producing and lactate-utilizing bacteria. Lactate is normally present at <3 mmol liter(-1) in stool samples from healthy adults, but concentrations up to 100 mmol liter(-1) have been reported in gut disorders such as ulcerative colitis. The effect of different initial pH values (5.2, 5.9, and 6.4) upon lactate metabolism was studied with fecal inocula from healthy volunteers, in incubations performed with the addition of dl-lactate, a mixture of polysaccharides (mainly starch), or both. Propionate and butyrate formation occurred at pH 6.4; both were curtailed at pH 5.2, while propionate but not butyrate formation was inhibited at pH 5.9. With the polysaccharide mix, lactate accumulation occurred only at pH 5.2, but lactate production, estimated using l-[U-(13)C]lactate, occurred at all three pH values. Lactate was completely utilized within 24 h at pH 5.9 and 6.4 but not at pH 5.2. At pH 5.9, more butyrate than propionate was formed from l-[U-(13)C]lactate in the presence of polysaccharides, but propionate, formed mostly by the acrylate pathway, was the predominant product with lactate alone. Fluorescent in situ hybridization demonstrated that populations of Bifidobacterium spp., major lactate producers, increased approximately 10-fold in incubations with polysaccharides. Populations of Eubacterium hallii, a lactate-utilizing butyrate-producing bacterium, increased 100-fold at pH 5.9 and 6.4. These experiments suggest that lactate is rapidly converted to acetate, butyrate, and propionate by the human intestinal microbiota at pH values as low as 5.9, but at pH 5.2 reduced utilization occurs while production is maintained, resulting in lactate accumulation.
Descripción8 pages, 3 figures, 4 tables.-- PMID: 17766450 [PubMed].
Versión del editorhttp://dx.doi.org/10.1128/AEM.00508-07
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