Microbial equol production attenuates colonic methanogenesis and sulphidogenesis in vitro

Anaerobe. 2010 Jun;16(3):247-52. doi: 10.1016/j.anaerobe.2010.03.002. Epub 2010 Mar 16.


Hydrogen gas produced during colonic fermentation is excreted in breath and flatus, or removed by hydrogen-consuming bacteria such as methanogens and sulphate-reducing bacteria. However, recent research has shown that H2 is also consumed by equol-producing bacteria during the reduction of daidzein into equol. In this study, the interactions between methanogens, sulphate-reducing, and equol-producing bacteria were investigated under in vitro simulated intestinal conditions. In the presence of daidzein, the equol-producing bacterial consortium EPC4 gave rise to equol production in cultures of Methanobrevibacter smithii or Desulfovibrio sp. as well as in faecal samples with methanogenic or sulphate-reducing abilities. Moreover, this supplementation significantly (P<0.001) decreased the methanogenesis and sulphidogenesis. The attenuation did not occur in the absence of a daidzein source. Additionally, there was no influence of soy germ powder, daidzein or equol as such, excluding a possible inhibition by these compounds. Finally, a stronger decrease was observed with increasing amounts of EPC4 and a constant equol production, suggesting that the observed effect was only partly caused by the action of daidzein as a hydrogen sink. These findings are of relevance since abdominal discomfort such as bloating and flatulence, are related to colonic gas production, whereas equol has potential health benefits.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Colon / metabolism*
  • Colon / microbiology*
  • Culture Media
  • Desulfovibrio / metabolism
  • Enterococcus faecium / growth & development
  • Enterococcus faecium / metabolism
  • Equol
  • Euryarchaeota / growth & development
  • Euryarchaeota / metabolism
  • Feces / microbiology
  • Female
  • Humans
  • Hydrogen / metabolism
  • Isoflavones / biosynthesis*
  • Isoflavones / metabolism
  • Lactobacillus / growth & development
  • Lactobacillus / metabolism*
  • Methane / metabolism*
  • Methanobrevibacter / growth & development
  • Methanobrevibacter / metabolism
  • Middle Aged
  • Sulfides / metabolism*
  • Veillonella / growth & development
  • Veillonella / metabolism


  • 4',7-dihydroxy-3,4-dihydroisoflavone
  • Culture Media
  • Isoflavones
  • Sulfides
  • Equol
  • daidzein
  • Hydrogen
  • Methane