Valerate production by Megasphaera elsdenii isolated from pig feces

Megasphaera elsdenii is able to produce several short-chain fatty acids (SCFAs), such as acetate, propionate, butyrate, and valerate. These SCFAs serve as an energy source for host animals and play an important role in gut health. In this study, M. elsdenii was isolated from pig feces that had been collected from two farms located in distinct areas of Japan. These M. elsdenii isolates were genotyped, and 7 representative strains were selected. When these 7 strains and M. elsdenii JCM 1772T were cultured with lactate for 24 h, all 7 strains produced valerate as a predominant SCFA. Therefore, the valerate-producing M. elsdenii inhabits a wide area of Japan. In contrast, M. elsdenii JCM 1772T produced acetate, propionate, butyrate, and valerate at similar levels. When the Y2 strain, one of the 7 representative strains, was cultured without lactate, low levels of valerate accumulated. In contrast, in a time course of lactate fermentation by the Y2 strain, lactate was rapidly consumed, and acetate and propionate were produced after 6 h of incubation. Thereafter, acetate and propionate were consumed from 6 to 12 h after the start of the incubation, and valerate and butyrate were produced. In most of the previously described M. elsdenii strains, valerate was not a predominant SCFA. Therefore, the M. elsdenii Y2 strain showed an unique metabolism in which valerate was produced as a primary end product of lactate fermentation.