Desorption of carbon dioxide from fermentation broth

Rates of CO 2 desorption from fermentation broths under actual operating conditions were determined by measuring the CO 2 partial pressure in the exit gas. The concentrations of CO 2 physically dissolved in the broths were measured by the so‐called tubing method. Values of k L a for CO 2 desorption calculated from these values agreed well with the k L a values for oxygen absorption corrected for the difference in gas diffusivities. The dissolved CO 2 concentration in the broth, which seems to bean important operating parameter, can easily be estimated from the CO 2 partial pressure in the exit gas, a more easily measurable quantity, if the k L a value is known. For a given value of k L a , assumption of perfect mixing or plug flow in the gas phase made little difference in the calculated values of the dissolved CO 2 concentration, indicating that the gas phase was probably in between perfect mixing and plug flow. In industrial fermentors, the CO 2 partial pressure in the exit gas can practically be assumed to be in equilibrium with the dissolved CO 2 concentration.