Liquid-film Time Constant Assessment for Kla Measurements in Respiring Fermentation Broths

To determine the liquid-film time constant (τF) of the dissolved oxygen electrode for kLa measurements with the dynamic method in respiring fermentation broths, an approach using the steady-state readings of the electrode in the broths containing respiring and non-respiring cells, respectively, has been established. The results showed that τF in microbial suspensions with high volumetric oxygen uptake rates could be very large under the conditions of low aeration and agitation, indicating the slower response of the oxygen electrode caused by the more difficult penetration of oxygen molecules through the thicker films with active cell respiration. The significance and adequacy of the τF corrections for kLa measurements were evaluated experimentally