Effect of Yeast Extract on Growth and Metabolism of H2-Utilizing Acetogenic Bacteria from the Human Colon |
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Authors: | Marion Leclerc Lila Elfoul-Bensaid Annick Bernalier |
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Institution: | (1) Laboratoire de Nutrition et Sécurité Alimentaire, INRA, Domaine de Vilvert, 78352 Jouy en Josas Cedex, France , FR |
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Abstract: | The aim of this work was to determine the effect of yeast extract and of its vitamin contents on autotrophic and heterotrophic
growth and metabolism of four acetogenic bacteria from the human colon. Yeast extract exerted a stimulatory effect on autotrophic
growth of the colonic acetogens, but concentration of this compound above 1–2 g. L−1 in the medium did not enhance utilization of H2/CO2. Vitamins provided by yeast extract were shown to be essential cofactors of the reductive pathway of acetate synthesis except
for one Clostridium strain. Yeast extract was also necessary to maintain heterotrophic growth and acetate synthesis from glucose in acetogenic
species, except in the Streptococcus strain. In the absence of yeast extract, vitamins could efficiently restore glucose fermentation via acetate. The reductive
and oxidative pathways of acetate synthesis might, therefore, depend on vitamin cofactors supplied by yeast extract in most
of the human acetogenic bacteria. Non-vitaminic factors appeared also to be involved in the metabolism of some of these acetogenic
species.
Received: 6 March 1998 / Accepted: 3 April 1998 |
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