On the applicability of the dynamic pressure step method for kLa determination in stirred Newtonian and non-Newtonian fluids, culture media and fermentation broths

Abstract

Determination of k L a by the dynamic pressure method (DPM) was carried out in different fluids by examining the raw signals of the measuring probes. Fluids included Newtonian and non-Newtonian shear-thinning solutions, two culture media and fermentation broths for gellan and xanthan production. The presence of a liquid film around the dissolved oxygen probe (DOP) membrane and the existence of a stable gas–liquid dispersion were the two main factors for k L a determination. When aeration resulted in extensive foam formation, the pressure step did not produce useful signals of the DOP and k L a determination was not possible. In Newtonian liquids, including culture media, the DPM was applicable for viscosities lower than 279 mPa s. In non-Newtonian fluids, the determination largely depends on the flow properties. In fermentation broths, determination was possible only when the oxygen consumption rate of the microorganism allowed to achieve steady state signals.