Effect of short-chain fatty acids on growth of the ruminal bacterium Streptococcus bovis.

Abstract

The effects of the sodium salts of acetic, propionic, butyric (volatile fatty acids, VFAs) and lactic acids on the growth of Streptococcus bovis JB1 were studied. Increasing concentrations (0.05-0.3 M) of VFAs or lactic acid produced progressive drops in the S. bovis growth rate. With concentrations of 0.1 M and higher, the inhibition was greater at pH 5.5 than at pH 6.5. Minimum relative growth rates of 0.65 and 0.56 were produced by 0.3 M of butyric (at pH 6.5) and lactic (at pH 5.5) acids, respectively. The inhibitory potency at pH 6.5 decreased in the order butyrate > propionate > acetate = lactate, while at pH 5.5 the order was lactate = butyrate > propionate > acetate. The inhibition elicited by acetate and lactate at pH 6.5 was similar to the inhibition caused by NaCI, but at pH 5.5, all the acids were more inhibitory than NaCI. Ethyleneglycol did not affect growth in any case. The effects of VFAs in mixtures seemed to differ from their effects when tested separately. It is suggested that the inhibitions observed resulted from both the increased ionic strength in the medium and the ability of the acids to solubilize in the bacterial membrane andl affect intracellular enzymes.The synergism of rumen microorganisms is complex. The existence of different metabolic roles in the rumen is well known, but the determination of the exact role of individual species is difficult. The rumen constitutes a system where the product of one type of microorganism may be the substrate of other species (5). Streptococcus bovis is a normal component of the rumen microbial ecosystem (24). This bacterium has, among other enzymatic activities, the ability to degrade both starch

Growth and pectate-lyase activity of the ruminal bacterium Lachnospira multiparus in the presence of short-chain organic acids

“…sugars, starch), high concentrations of this acid may appear in the rumen as an end product of microbial fermentation (Counotte and Prins 1979). In spite of VFA and lactic acid being found commonly in the rumen, little is known about their effect on the ruminal microbial populations and/or their enzymatic activities (Fay and Ovejero 1986; Paggi and Fay 1996; Russell and Diezgonzalez 1998; Paggi et al. 1999a,b, 2004).…”