Determination of mixing time in a disposable bioreactor supported with wave-induced agitation

Authors:

• Mateusz Bartczak,
• Aleksandra Raczkowska,
• Kamil Wierzchowski,
• Maciej Pilarek

Abstract

Bioreactors equipped with disposable (i.e. single-use) culture bags are alternatives to equipment supported with steel- or glass-made culture vessels. Wave-type agitated bioreactors are the most popular group of disposable bioreactors. Such non-typical kind of agitation is induced by oscillatory rocking movements of the whole single-use vessel. The wave-type agitation is widely recognized as a low shear stress process, and it is particularly recommended for bioprocessing of fragile types of biomass, i.e. animal or plant cells/organs, which can be easily destroyed by typical spinning stirrers applied for mechanical mixing of culture systems. The aim of the study was to recognize the influence of operational parameters defining the wave-type agitation intensity on values of mixing time (𝜏 ) reached in ReadyTo- Process WAVE™ 25 bioreactor. The impact of four operational parameters has been investigated: (i) angle (2–12°) and (ii) frequency of oscillations (2–40 rpm), (iii) rocking motion (30–90%), and (iv) volume of the aqueous phase (0.2– 1.0 dm3) inside the vessel. The design of experiments (DoE) methodology has been applied for distinguishing operating parameters as relevant or irrelevant ones. The two experimental methods have been applied for independent validation of 𝜏 values reached in the studied system: the standard decolorization method and the sensor method of pH level monitoring during neutralization reaction. The results unequivocally exhibited predominance of the sensor vs. decolorization method in the case of accurate and repeatable determination of 𝜏 . The angle and the frequency of oscillations, and the volume of the aqueous phase impacted significantly on 𝜏 , with the highest influence of the frequency of oscillations. The impact of the rocking motion parameter was statistically irrelevant.