With the increased production of biodiesels, large amounts of glycerol are produced as a byproduct with limited use, causing a significant environmental problem. It is thus desirable to use this waste glycerol as a renewable feedstock to produce industrial chemicals and fuels to replace fossil fuels and petrochemicals. Our previous study indicates that Propionibacterium acidipropionici can convert glycerol to propionic acid at high yield and high purity, but with a very low productivity. In this work, the effect of carbon dioxide on the propionic acid productivity was studied. Based on the metabolic analysis, CO₂ (HCO₃^-) is required in the Wood-Werkman cycle which determines the propionic acid synthesis. Carbon dioxide, with phosphoenolypyruvate (PEP) is converted to oxalacetate by the enzyme phosphoenolypyruvate carboxylase. Through several sequential reactions, oxalacetate is finally converted to propionic acid. It is found that the productivity of propionic acid with CO₂ (HCO₃^-) is 2.94 g/l/day, which is much higher than that without CO₂ (HCO₃^-) (1.56 g/l/day). However, the yield of propionic acid is decreased slightly from 0.77 to 0.67 g/g glycerol due to the higher biomass production. In addition, the yield and productivity of succinate, the main intermediate in Wood-Werkman cycle, is increased by 81% and 280%, respectively. These results imply the increase in the Wood-Werkman cycle rate because of the addition of CO₂ (HCO₃^-). Thus, the activities of key enzymes (e.g. phosphoenolypyruvate carboxylase, oxaloacetate transcarboxylase, and propionyl CoA transferase) involved in the Wood-Werkman cycle were also studied in this work.