Growth rates and culture conditions affect the molar yields of catabolic end products and cells of Succinivibrio dextrinosolvens growing on glucose. When growth in chemostats occurred, a trend toward decreased succinate and acetate formation, increased lactate formation, and a higher yield of cells correlated with an increase in the growth rate. End product and cellular yields on defined medium indicate a high maintenance requirement for S. dextrinosolvens and are consistent with energy conservation steps during the formation of acetate and succinate. Simultaneous carbon dioxide consumption and production were determined from batch studies with NaH14CO3, and the amounts were used to calculate a fermentation balance. These data also indicated that CO2 consumption lags behind CO2 production early in the growth phase, becoming equivalent to it toward stationary phase. Significantly more CO2 was fixed by S. dextrinosolvens when the organism was cultured in chemostats sparged with CO2. Formate is in part derived from free CO2 in the medium, as shown by 13C nuclear magnetic resonance studies, and may be sensitive to CO2 availability. Nuclear magnetic resonance data are consistent with the carboxylation of a C3 intermediate of the Embden-Meyerhof-Parnas pathway of glycolysis to a C4 compound to eventually form succinate.