The mechanism of propionic acid formation by Clostridium propionicum.

CZostridium propionicum evidently possesses a mechanism for the conversion of lactate to propionate different from that found in the previously studied propionic acid producing bacteria. Reactions common to certain propionibacteria and VeiZZoneZZa gazogenes which could not be demonstrated with Cl. propionicum include : ( a ) the decarboxylation of succinic acid ; (b) the fermentation of malate and fumarate ; (c) the variation in the ratio of acetic to propionic acid according to the concentration of CO,; (d) the fixation of CO, in propionic acid.