ROLE OF EXTRACELLULAR ACETATE IN THE FERMENTATION OF GLUCOSE BY A RUMINAL BACTERIUM, MEGASPHAERA-ELSDENII

In batch culture, addition of acetate stimulated the initial growth of Megasphaera elsdenii in medium containing glucose and Trypticase. As the initial concentration of acetate was increased, butyrate production increased. When acetate was used, the rate of butyrate production increased. Hydrogen production was decreased by adding acetate. Inhibition of hydrogen production by the hydrogenase inhibitor carbon monoxide inhibited the growth of M. elsdenii, but this inhibition was cancelled by adding acetate. In continuous culture, where the growth rate was kept relatively low by limiting the glucose supply, adding acetate similarly increased butyrate production. These results suggest that acetate serves as an electron sink in M. elsdenii.