Effect of elevated dissolved carbon dioxide concentrations on growth of Corynebacterium glutamicum on d-glucose and l-lactate

The effect of increased dissolved carbon dioxide concentrations on growth of Corynebacterium glutamicum was studied with continuous turbidostatic cultures. The carbon sources were either l-lactate or d-glucose. To increase the dissolved carbon dioxide concentration the carbon dioxide partial pressure of the inlet gas stream p C O 2 , IN was increased stepwise from 0.0003 bar (air) up to 0.79 bar, while the oxygen partial pressure of the inlet gas stream was kept constant at 0.21 bar. For each resulting carbon dioxide partial pressure p C O 2 the maximum specific growth rate μ max was determined from the feed rate resulting from the turbidostatic control. On d-glucose and p C O 2 up to 0.26 bar, μ max was mostly constant around 0.58 h −1. Higher p C O 2 led to a slight decrease of μ max. On l-lactate μ max increased gradually with increasing carbon dioxide partial pressures from 0.37 h −1 under aeration with air to a maximum value of 0.47 h −1 at a p C O 2 of 0.26 bar. At very high p C O 2 (0.81 bar) μ max decreased down to 0.35 h −1 independent of the carbon source.