A simple eccentric stirred tank mini‐bioreactor: Mixing characterization and mammalian cell culture experiments

Abstract

In industrial practice, stirred tank bioreactors are the most common mammalian cell culture platform. However, research and screening protocols at the laboratory scale (i.e., 5-100 mL) rely primarily on Petri dishes, culture bottles, or Erlenmeyer flasks. There is a clear need for simple-easy to assemble, easy to use, easy to clean-cell culture mini-bioreactors for lab-scale and/or screening applications. Here, we study the mixing performance and culture adequacy of a 30 mL eccentric stirred tank mini-bioreactor. A detailed mixing characterization of the proposed bioreactor is presented. Laser induced fluorescence (LIF) experiments and computational fluid dynamics (CFD) computations are used to identify the operational conditions required for adequate mixing. Mammalian cell culture experiments were conducted with two different cell models. The specific growth rate and the maximum cell density of Chinese hamster ovary (CHO) cell cultures grown in the mini-bioreactor were comparable to those observed for 6-well culture plates, Erlenmeyer flasks, and 1 L fully instrumented bioreactors. Human hematopoietic stem cells were successfully expanded tenfold in suspension conditions using the eccentric mini-bioreactor system. Our results demonstrate good mixing performance and suggest the practicality and adequacy of the proposed mini-bioreactor.

Studying Mixing in Non-Newtonian Blue Maize Flour Suspensions Using Color Analysis

“…Figure 4 illustrate these findings, showing different mixing conditions or states in a stirred tank containing a blue maize non-Newtonian flour suspension. In Figure 4a , which depicts a tank stirred by an eccentrically located inclined disc impeller [36] , [37] , a subsurface acid injection was efficiently dispersed to achieve a practically (at least visually) homogeneous condition in less than 5 minutes. In Figure 4b , we show the final state of mixing of a similar experiment.…”

The simplest stirred tank for laminar mixing: Mixing in a vessel agitated by an off‐centered angled disc

“…This suggests that the stirring configuration studied here would provide adequate mixing in laminar vessels at lower RPM values (and consequently lower tip speed values) than other configurations. This can be very useful in the context of culture of shear‐sensitive cells, such as CHO cells, stem cells, plant cells, and fungus broths (see also Bulnes‐Abundis et al, 2012) . In practice, this also implies adequate mixing at lower power input and shear stress.…”

“…Laminar mixing scenarios are not uncommon in industrial practice. Some relevant examples are the agitation of high‐viscosity materials in the food industry and in the manufacture of lubricants, the formulation of cosmetics such as creams and unguents, the mixing of liquid detergents, and the agitation of shear‐sensitive cells (fungi, plant, insect, and animal cells) in the biopharmaceutical/biotechnology industries . In the specific case of biotechnology applications, and particularly in laboratory‐scale experiments (for the screening of cell culture conditions, the selection of high‐producing clones, or the definition of culture medium, etc.…”

“…In the specific case of biotechnology applications, and particularly in laboratory‐scale experiments (for the screening of cell culture conditions, the selection of high‐producing clones, or the definition of culture medium, etc. ), mixing at low speed is desirable . Nevertheless, stirred tanks are (by far) the most widely used mixing system, even though conventional stirred tank configurations are not well‐suited for laminar mixing.…”

The impact of chaotic advection on the microstructure of polymer‐modified bitumen

“…This approach unveiled a surprisingly rich dynamics of the mixing process even in remarkably simple flows, thus establishing a strong connection between chaotic behavior of fluid element trajectories and mixing efficiency . Based on these concepts, the possibility of obtaining efficient mixing in stirred tanks processing highly viscous fluid was extensively investigated in a series of works, which identified symmetry‐breaking of the equipment geometry as one of the most effective routes to massive chaotic behavior . For instance, in contrast to what a naive, intuition‐based approach would suggest, it was showed that whenever laminar regime prevails, an eccentric placement of the stirrer in a cylindrical vessel could shrink down the mixing time by orders of magnitude when compared to the standard symmetric configuration.…”