title: Lactate is mainly fermented to butyrate by human intestinal microfloras but inter-individual variation is evident.
abstract: OBJECTIVE
  To assess the role of lactate as a precursor for butyrate biosynthesis in human colonic microflora.
  
  
  RESULTS
  Three human faecal microfloras were incubated in vitro with media supplemented with 30 mmol l(-1) unenriched or 13C-enriched lactate. Lactate metabolism and short-chain fatty acid (SCFA) production were quantified. Lactate conversion to butyrate was investigated by gas chromatography-mass spectrometry and the pathways involved were identified by 13C nuclear magnetic resonance spectroscopy. All human faecal microfloras rapidly and completely fermented lactate, yielding approx. 19 mmol l(-1) total SCFAs. However, the SCFA composition varied markedly between microfloras. Butyrate was the main end-product for two microfloras but not for the third (60 and 61%vs 27% of the net concentration of SCFA produced respectively). The latter was typified by its ability to produce propionate as a major product (37%), and valerate (3%). 13C-Labelling showed that butyrate was produced through the acetyl-CoA pathway and that the three microfloras possessed significant differences in their metabolic pathways for lactate consumption.
  
  
  CONCLUSIONS
  In contrast to the ruminal microflora, the human intestinal microflora can utilize both d- and l-lactate as precursors for butyrate synthesis. Inter-individual variation is found.
  
  
  CONCLUSIONS
  This study suggests that the butyrogenic capability of colonic prebiotics could be related to lactate availability. These findings will direct the development of selection strategies for the isolation of new butyrate-producing bacteria among the lactate-utilizing bacteria present in the human intestinal microfloras.
authors.affiliation: Human Nutrition Research Centre, UFDNH - INRA, Nantes cedex 03, France.
authors.forename: C
authors.initials: C
authors.lastname: Bourriaud
authors.forename: R J
authors.initials: RJ
authors.lastname: Robins
authors.forename: L
authors.initials: L
authors.lastname: Martin
authors.forename: F
authors.initials: F
authors.lastname: Kozlowski
authors.forename: E
authors.initials: E
authors.lastname: Tenailleau
authors.forename: C
authors.initials: C
authors.lastname: Cherbut
authors.forename: C
authors.initials: C
authors.lastname: Michel
mesh_terms: D000328:Adult; D020148:Butyric Acid / Q000378:metabolism*; D003106:Colon / Q000382:microbiology*; D005232:Fatty Acids, Volatile / Q000096:biosynthesis; D005243:Feces / Q000382:microbiology; D005260:Female; D005285:Fermentation / Q000502:physiology; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D008875:Middle Aged
chemical_list: D005232:Fatty Acids, Volatile; D020148:Butyric Acid; D019344:Lactic Acid