The effect of Saccharomyces cerevisiae on in vitro growth and fermentation of Selenomonas ruminantium and Megasphaera elsdenii

Abstract

Stimulation of lactate utilization by Selenomonas ruminantium and Megasphaera elsdenii may help in reducing problems associated with rumen acidosis. The objective of this study was to determine the effect of a Saccharomyces cerevisiae live culture and Saccharomyces cerevisiae fermentation products on in vitro growth and fermentation of lactate-utilizing ruminal bacteria, S. ruminantium (ATCC 19205) and M. elsdenii (ATCC 25940). The cultures were run for 0, 6, 12, 24 and 48 h under anaerobic conditions on a growth medium supplemented with a yeast live culture (SC) or with yeast fermentation products (SCFP) and, as reference, on the same medium without supplementation (CON). Neither SC nor SCFP had a significant effect on the growth of S. ruminantium after 6, 12 and 24 h of incubation, but the live yeast culture significantly (P≤0.05) improved the growth of these bacteria after 48 h of incubation. The yeast fermentation products significantly (P≤0.05) decreased pH and increased lactate synthesis by S. ruminantium. The Saccharomyces cerevisiae live culture significantly improved the growth of M. elsdenii after 12 and 24 h of incubation, and the S. cerevisiae fermentation products increased its growth after 48 h. The After 24 and 48 h of incubation the Saccharomyces cerevisiae live culture reduced the concentration of total volatile fatty acids (VFA), while caproate was the main product of in vitro fermentation of M. elsdenii (P≤0.05). Saccharomyces cerevisiae live cultures may improve microbial fibre fermentation in the rumen by maintaining optimal pH conditions.