Effects of a strain of Saccharomyces cerevisiae (Levucell® SC), a microbial additive for ruminants, on lactate metabolism in vitro

Abstract

The effect of Levucell SC, a strain of Saccharomyces cerevisiae marked as a feed additive for ruminants, was investigated in vitro on lactate metabolism by the ruminal bacteria Streptococcus bovis and Megasphaera elsdenii. The coculture between 10(7) live cells x mL(-1) of SC and a Streptococcus bovis strain in the presence of glucose reduced lactate production by the bacterial strain. Live yeast cells were able to compete with Streptococcus bovis for glucose utilization in strictly anaerobic conditions, so less glucose was available for the bacterium. SC also stimulated L-lactate utilization by a strain of M. elsdenii. The effect depended on the concentration of yeast cells added. Bacterial growth and fermentation end-product concentrations were also increased in the presence of SC. Some amino acids and vitamins, but not dicarboxylic acids, stimulated the bacterial specific activity of L-lactate uptake. SC was able to provide amino acids to M. elsdenii. In a coculture of Streptococcus bovis and M. elsdenii on glucose, the reduction of lactate concentration was improved by SC, the same trend being observed when maltose or soluble starch were used as carbon and energy source. These results indicate that SC can be a very useful tool to reduce lactate accumulation in vitro during fermentation of soluble sugars.

Effects and modes of action of live yeasts in the rumen

“…Effects of live yeasts have been extensively studied on lactate-metabolizing bacteria. In vitro, one strain of S. cerevisiae was able to outcompete S. bovis for the utilization of sugars; the reduction in quantity of fermentable sugars available for the bacteria consequently limited the amount of lactate produced (Chaucheyras et al, 1996). This effect was only observed when the yeast cells were alive.…”

“…Dead cells had no effect on lactate production. Moreover, stimulation of growth and metabolism of lactate-utilizing bacteria, such as Megasphaera elsdenii or Selenomonas ruminantium was observed in vitro in the presence of different live yeasts (ADY or YC) (Nisbet & Martin, 1991;Rossi et al, 1995;Chaucheyras et al, 1996;Newbold et al, 1998;Rossi et al, 2004) through a supply of different growth factors, such as amino acids, peptides, vitamins, and organic acids, essential for the lactate-fermenting bacteria. The impact of yeast probiotics on ruminal lactate concentration has been confirmed in several in vivo studies.…”

The effect of basal diet on lactate-producing bacteria and the susceptibility of sheep to lactic acidosis

“…Several methods are used to reduce the risk of acidosis, including the use of buffers such as sodium bicarbonate (Dunn et al, 1979;Kezar and Church, 1979), inclusion of dietary clays such as bentonite (Huntington et al, 1977;Dunn et al, 1979), the use of antibiotic food additives such as virginiamycin (VM; Godfrey et al, 1995;Rogers et al, 1995) or certain ionophores (Nagaraja et al, 1981 and1985), use of microbial food additives, such as Megasphaera elsdenii , which ferment lactate (Kung and Hession, 1995;Wiryawan and Brooker, 1995) or Saccharomyces cerevisiae (Chaucheyras et al, 1996) as well as the conventional method of gradual introduction of grains. In order to be able to prevent acidosis without further interruption to the fermentation system it is important to identify the rôle of the basal diet with regard to microbial adaptability.…”

Stimulation of the Megasphaera elsdenii’s butyrate production in continuous culture by a yeast additive

“…The volatile fatty acids (VFA, acetate, propionate and butyrate) are the main products of lactate metabolism (Marounek & Bartos, 1987;Marounek et al, 1989;Hino et al, 1994). On the other hand, the effect of additives on microbial activity has been reported (Wallace & Newbold, 1992), both growth and lactate uptake are stimulated by the commercial additives: Amaferm (Waldrip & Martin, 1993), Yea Sacc (Rossi et al, 1995) and Levucell SC (Chaucheyras et al, 1996). Nevertheless, their effect on microbial fermentation patterns are not well known.…”