IN-VITRO H-2 UTILIZATION BY A RUMINAL ACETOGENIC BACTERIUM CULTIVATEDALONE OR IN ASSOCIATION WITH AN ARCHAEA METHANOGEN IS STIMULATED BY APROBIOTIC STRAIN OF SACCHAROMYCES-CEREVISIAE

The effects of a live strain of Saccharomyces cerevisiae on hydrogen u tilization and acetate and methane production by two hydrogenotrophic ruminal microorganisms, an acetogenic bacterial strain and an archaea methanogen, were investigated. The addition of yeast cells enhanced by more than fivefold the hydrogenotrophic metabolism of the acetogenic strain and its acetate production. In the absence of yeasts, and in a coculture of the acetogen and the methanogen, hydrogen was principally used for methane synthesis, but the presence of live yeast cells stim ulated the utilization of hydrogen by the acetogenic strain and enhanc ed acetogenesis.