New Insights from Locally Resolved Hydrodynamics in Stirred Cell Culture Reactors

Fabian Freiberger,Jens Budde,Michael Schlüter,Ralf Pörtner,Johannes Möller,Eda Ateş

doi:10.3390/pr10010107

Fabian Freiberger, Jens Budde + Show 4 more

Open Access

https://doi.org/10.3390/pr10010107

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Journal: Processes	Publication Date: Jan 5, 2022
Citations: 10	License type: CC BY 4.0

Affiliation: Universität Hamburg, Hamburg University of Technology

Abstract

The link between hydrodynamics and biological process behavior of antibody-producing mammalian cell cultures is still not fully understood. Common methods to describe dependencies refer mostly to averaged hydrodynamic parameters obtained for individual cultivation systems. In this study, cellular effects and locally resolved hydrodynamics were investigated for impellers with different spatial hydrodynamics. Therefore, the hydrodynamics, mainly flow velocity, shear rate and power input, in a single- and a three-impeller bioreactor setup were analyzed by means of CFD simulations, and cultivation experiments with antibody-producing Chinese hamster ovary (CHO) cells were performed at various agitation rates in both reactor setups. Within the three-impeller bioreactor setup, cells could be cultivated successfully at much higher agitation rates as in the single-impeller bioreactor, probably due to a more uniform flow pattern. It could be shown that this different behavior cannot be linked to parameters commonly used to describe shear effects on cells such as the mean energy dissipation rate or the Kolmogorov length scale, even if this concept is extended by locally resolved hydrodynamic parameters. Alternatively, the hydrodynamic heterogeneity was statistically quantified by means of variance coefficients of the hydrodynamic parameters fluid velocity, shear rate, and energy dissipation rate. The calculated variance coefficients of all hydrodynamic parameters were higher in the setup with three impellers than in the single impeller setup, which might explain the rather stable process behavior in multiple impeller systems due to the reduced hydrodynamic heterogeneity. Such comprehensive insights lead to a deeper understanding of the bioprocess.

Highlights

Mammalian cell culture processes are state-of-the-art for the production of therapeutic antibodies
The hydrodynamics, mainly flow velocity, shear rate and power input, in a single- and a three-impeller bioreactor setup were analyzed by means of computational fluid dynamics (CFD) simulations, and cultivation experiments with antibody-producing Chinese hamster ovary (CHO) cells were performed at various agitation rates in both reactor setups
It was examined to what extent the observed effects can be explained on the basis of the hydrodynamic parameters determined via CFD simulations, where mainly the fluid velocity, power input, or energy dissipation rate were considered

Summary

Introduction

Mammalian cell culture processes are state-of-the-art for the production of therapeutic antibodies. Common methods for scaling-up mammalian cell-based production processes aim to keep the reactor geometry and certain process parameters such as the average volumetric power input constant [7,8,9,10,11]. These “rules of thumb” methods are limited as they can hardly be used to describe or estimate an appropriate operation range with respect to shear effects on cellular behavior. Constant cell specific growth rate, μmax, over a broader stirrer operation range in reactor systems with multiple impellers compared to reactor systems with only one impeller. Shear effects seem to be less pronounced in the case of multiple impellers

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