Ra. Paggi et Jp. Fay, EFFECT OF SHORT-CHAIN FATTY-ACIDS ON GROWTH OF THE RUMINAL BACTERIUM STREPTOCOCCUS-BOVIS, Journal of General and Applied Microbiology, 42(5), 1996, pp. 393-400
The effects of the sodium salts of acetic, propionic, butyric (volatil
e fatty acids, VFAs) and lactic acids on the growth of Streptococcus b
ovis 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 a
t pH 5.5 than at pH 6.5. Minimum relative growth rates of 0.65 and 0.5
6 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 th
e order butyrate > propionate > acetate = lactate, while at pH 5.5 the
order was lactate = butyrate > propionate > acetate. The inhibition e
licited by acetate and lactate at pH 6.5 was similar to the inhibition
caused by NaCl, but at pH 5.5, all the acids were more inhibitory tha
n NaCl. Ethyleneglycol did not affect growth in any case. The effects
of VFAs in mixtures seemed to differ from their effects when tested se
parately. 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 and affect intracellula
r enzymes.