Impact of operating parameters on values of a volumetric mass transfer coefficient in a single-use bioreactor with wave-induced agitation

Abstract

The knowledge of a volumetric liquid-side mass transfer coefficient (kLa) characterizing the oxygen transfer in bioreactor working at defined operating parameters, is a fundamental principle for establishing the aeration strategy for aerobic bioprocesses. The design of experiments (DoE) methodology has been applied for distinguishing relevant from irrelevant operating parameters, and for prediction of characteristics of oxygen mass transfer effects, in the whole range of values of operating parameters accessible in setup of ReadyToProcess WAVE™ 25 (WAVE 25; GE Healthcare) bioreactor equipped with 2dm3 disposable culture bag. Due to DoE-aided analysis, rocking speed (ω), rocking angle (α) and volumetric flow of gas phase through the culture bag (QG) have been indicated as the operating parameters robustly impacting on the value of the kLa coefficient. All relevant operational parameters, i.e. ω, α and QG, exerted monotonically increasing influence on kLa. Otherwise, the influence of volume of liquid poured into culture bag (VL) and oxygen partial pressure in applied gas phase (p1) on kLa proved to be negligible. Two original correlations have been proposed to generalize the experimental results and to estimate the kLa coefficient values possible to be reached in the WAVE 25: the dimensional correlation defining the kLa coefficient, as well as the dimensionless correlation that defines Sherwood number and integrating the originally-defined Reynolds number for the liquid phase that is subjected to wave-induced mixing. The validity of results predicted by both correlations has been verified by acceptable level of the relative errors.