摘要：Lactate is seldom detected as a major acid in the hindgut because it is a typical intermediate metabolite and is converted to a short-chain fatty acid (SCFA) by lactate-utilizing bacteria. Lactate becomes a key metabolite in the large intestine when lactogenic and bifidogenic dietary supplements are fed to animals. If lactate-utilizers are eliminated, lactate will be accumulated. Accumulation of lactate in hindgut might be responsible for diarrhoea caused by short-bowel syndrome, dyspepsia, and antibiotic treatments. Thus, the lactate metabolism in the hindgut ecosystem is important. L-[3-13C]-lactate fermentation was studied in a pig in vitro model using 13C-NMR. Pig cecal digesta were diluted with four weights of an anaerobic phosphate buffer containing 13C-labeled lactate. The mixture was incubated for 24 h at 37°C with gentle shaking. A portion of the culture was sampled periodically and analysed for SCFA. [3-13C] propionate, [2-13C] acetate, [2-13C] propionate, [2-13C] butyrate, and [4-13C] butyrate were produced from [3-13C]-Lactate in decreasing order. The importance of an acrylate pathway in propionate formation was evidenced by the predominant [3-13C] propionate formation. An equal production of [2-13C] butyrate and [4-13C] butyrate, as well as a negligible production of [3-13C] butyrate, indicated that extra non-labeled acetate is required for butyrate synthesis. 13C-labelled butyrate, together with the detection of [2-13C] valerate, suggested the important role for Megasphaera elsdenii in lactate utilization in the system.Keywords: 13C-NMR, lactate metabolism, large intestine, pig.
