The Growth Response of Cellulolytic Acetate-utilizing and Acetate-producing Butyrivibrios to Volatile Fatty Acids and Other Nutrients

Abstract

SUMMARY: The growth responses of 33 strains of cellulolytic butyrivibrios, isolated from the rumens of sheep fed on low-protein teff hay diets, to various combinations of volatile fatty acids (VFA) have been determined. Propionate alone was generally retardatory to the acetate-utilizing strains whilst acetate was stimulatory. Branched-chain VFA were generally stimulatory to those strains on which propionate had a retardatory effect, and retardatory to those strains on which propionate had no effect. Propionate alone was generally stimulatory to the acetate-producing strains and the effect of acetate and branched-chain VFA was variable. The major nutrient requirements of a few selected acetate-utilizing and acetate-producing strains are presented. A chemically defined medium was formulated which permits as good growth as a rumen-fluid medium for the acetate-utilizing butyrivibrios, Ruminococcus albus and Cillobacterium cellulosolvens.