This study presents an in-depth study on the physiological behavior of Mannheimia succiniciproducens, a capnophilic bacterium and an efficient succinic acid producer, under varying gas conditions as H(2) and CO(2) play important roles in the production of succinic acid. Constraints-based flux analysis of the genome-scale metabolic model of M. succiniciproducens was performed to estimate the production patterns of several organic acids in response to varying H(2), CO(2), and glucose uptake rates. Results from controlled cultivations performed previously and constraints-based flux analyses of M. succiniciproducens in this study revealed that there is an optimal range of CO(2) level in the medium for enhancing cell growth and succinic acid production at a given glucose uptake rate. Furthermore, the uptake rates of H(2) and CO(2) from the medium have a direct relationship with each other, significantly influencing the rates of cell growth and succinic acid production. Predictions made in this study quantitatively describe the physiological changes of the cell in response to varying H(2), CO(2), and glucose uptake rates, which consequently allow us to identify the feasible physiological states of the cell with respect to cell growth rate and succinic acid production rate.