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 pCO2,INpCO2,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 pCO2pCO2 the maximum specific growth rate μmax was determined from the feed rate resulting from the turbidostatic control. On d-glucose and pCO2pCO2 up to 0.26 bar, μmax was mostly constant around 0.58 h−1. Higher pCO2pCO2 led to a slight decrease of μmax. On l-lactate μmax 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 pCO2pCO2 of 0.26 bar. At very high pCO2pCO2 (0.81 bar) μmax decreased down to 0.35 h−1 independent of the carbon source.