The Probiotic Strain Clostridium butyricum TO-A Produces Butyrate by Utilizing Lactate and Acetate

Lactate-utilizing bacteria (LUB) are intestinal bacteria that produce butyrate from lactate and acetate, key metabolites in the gut. As LUB help maintain lactate and butyrate concentrations in the intestinal tract, they are promising probiotic candidates. Clostridium butyricum TO-A (CBTOA) has reportedly been effective in treating various gastrointestinal issues in humans and animals. Although CBTOA is known to increase intestinal butyrate levels, it is unclear how it utilizes lactate and acetate, similar to LUB, to produce butyrate. We investigated lactate utilization-related genes in CBTOA and examined the relationship between lactate and acetate utilization and butyrate production using peptone-yeast medium supplemented with D-lactate, L-lactate, and/or acetate. This study demonstrates for the first time that the probiotic strain CBTOA harbors lactate utilization-related genes and efficiently produces butyrate only in the presence of exogenous lactate and acetate instead of sugars. Furthermore, CBTOA expresses a lactate racemase that enables the bacterium to utilize both lactate enantiomers while regulating the ratio of D-lactate to L-lactate in the intestinal microenvironment via racemization. In conclusion, CBTOA efficiently produces butyrate utilizing lactate and acetate, similar to LUB; therefore, CBTOA could be an efficient butyrate supplier as a probiotic strain in the intestinal tract.