Optimization of culture conditions in CO 2 fixation for succinic acid production using Actinobacillus succinogenes

The culture conditions in CO2 fixation by Actinobacillus succinogenes for succinic acid production were investigated by a model of available CO2 in a 3-l fermentor. The results from the model analysis showed that the available CO2 for succinic acid production in the fer- mentation broth is the sum of HCO3 - ,C O 3 2- , and CO2 influenced by external culture conditions such as medium components, CO2 partial pressures, and temperature. The optimized conditions for CO2 supply in a 3-l fermentor were determined as follows: CO2 partial pressure and stirring speed were maintained at 0.1 MPa and 200 r min -1 , respectively, with a pH of 6.8 and a temperature of 37C; 0.15 mol l -1 NaHCO3 was added. Under the optimized conditions, a CO2 fixation rate of 0.57 g l -1 h -1 was obtained, and a succinic acid concentration of 51.6 g l -1 with a yield of 75.8% was reached. These results suggest that optimized conditions of CO2 supply are effective in high succinic acid production and thus have potential applications in succinic acid production and CO2 fixation.