Continuous culture study of the ruminal bacterium Megasphaera elsdenii using lactate as carbon source is reported. Butyrate, the minor product in batch culture, was the main product in continuous culture. Under steady state conditions the biomass concentration was increased from 0.46 to 0.72 g l-1. Addition of Yea Sacc did not result an increased availability of carbon. The produced amounts of valerate and CO2 were calculated by using a combined carbon and degree of reduction balances. According to these results, the lactate catabolism of M. elsdenii was changed by the presence of yeast additive, yielding more butyrate and diminishing the production of valerate, while acetate and propionate production was not affected. Results reported in this work suggested that soluble compounds present in the yeast additive filtrate enhanced the anabolism of M. elsdenii and modified the carbon fluxes through its pathways by increasing butyrate and decreasing valerate production in continuous culture.
Megasphaera elsdenii; butyrate; yeast additive; continuous culture
