Agitation, aeration and perfusion modules for cell culture bioreactors

Abstract

For an optimized bioreactor design which is adapted to the cultivation of sensitive animal cells different modular bioreactor components for gentle agitation, sufficient aeration and long-term perfusion were developed and investigated with respect to their suitability from laboratory to production scale. Aeration systems have been designed for both shear sensitive cells and cells which tolerate bubbles. The systems are based on either membranes for bubble-free aeration or stainless steel sparger systems. They were characterized by determination of their oxygen transfer capacity and optimized in cultivation processes of different cell lines under process conditions such as batch and perfusion mode. Different impellers for suspension cells and cells grown on carriers were investigated for their suitability to ensure homogeneous gentle mixing. A large pitch blade impeller as well as a novel 3-blade segment impeller are appropriate for homogeneous mixing at low shear rates. Especially with the 3-blade segment impeller fluid mechanical stress can be reduced at a given stirrer speed which is advantageous for the cultivation of cells attached to microcarriers or extremely shear sensitive suspension cells. However, our results indicate that shear sensitivity of animal cells has been generally overestimated. Continuous perfusion of both suspension cell cultures and cells cultivated on microcarriers could be successfully performed over extended periods of time using stainless steel spinfilters with appropriate pore sizes and systems based on microporous hydrophilic membranes. Spinfilters are suitable cell retention systems for technical scale bioreactors allowing continuous perfusion cultures of suspension cells (pore size 10 to 20 microns) as well as anchorage dependent cells grown on microcarriers (pore size 75 microns) over six weeks to 3 months. Applying the developed modules for agitation, aeration and perfusion process adapted bioreactor set-ups can be realized which ensure optimum growth and product formation conditions in order to maximize cell and product yields.

Microwell engineering characterization for mammalian cell culture process development

“…The predicted k L a values obtained here for 24-SRW plates are summarized in Table II. The k L a values under all conditions investigated were greater than 1 h À1 which is the value generally considered sufficient to support the oxygen demand of 10 6 to 10 7 cells mL À1 (Fenge et al, 1993). The highest value predicted, 29 h…”

CFD for Characterizing Standard and Single-use Stirred Cell Culture Bioreactors

“…Although there are some doubts from the fluid dynamic perspective, maximum tolerable tip speeds are described in the literature [Fenge, et al (1993); Varley & Birch (1999)]. Maximum tolerable tip speeds differ between cell lines: hybridoma cells were found to tolerate the highest values of up to 1.8 m·s -1 [Chisti (2001)].…”

Evaluation of membranes for use in on-line cell separation during mammalian cell perfusion processes

“…These devices can be placed into the bioreactor or in an external loop. As internal systems spin filters (rotating sieves) (Fenge et al, 1993) and membrane devices proved to be successful (Bfintemeyer et al, 1987). Synthetic membranes can be used as hollow fibres or flat membranes in an arrangement of static or cross flow elements.…”