Cell retention techniques

Voisard, D., F. Meuwly, P.A. Ruffieux, G. Baer, and A. Kadouri. 2003. Potential of cell retention techniques for large-scale high-density perfusion culture of suspended mammalian cells. Biotechnol Bioeng 82 751-765. 

The fed-batch and batch cultivation systems share the same cleaning and sterilization process in which the bioreactor operation is stopped and the bioreactor is emptied. This stoppage creates considerable costs and operational downtime. The repeated or cyclic system, which can be applied to both batch and fed-batch cultivation systems, may be installed in order to maximize the productivity. The cyclic cultivation system does not enter the cleaning and sterilization process, but rather empties a portion of the bioreactor while preserving part of the batch for the next cycle. Another method to increase productivity is cell retention techniques such as fluidized beds, membranes, or external separators. These options allow multiple cycles without cleaning and sterilization, which is initiated only if it is deemed that mutation risks exceed tolerable levels (Bellgardt, 2000b). 

B.5 CELL RETENTION TECHNIQUES FOR USE IN CONTINUOUS OPERATION IN SUSPENDED CELL PERFUSION PROCESSES... 

B.5.1 Cell Retention Based on Size Different Types of Filtration Techniques... 

Lee, W. G., Lee, Y. S., Chang, H. N., Chang, Y. K. (1994). A cell retention internal filter reactor for ethanol production using tapioca hydrolysates. Biotechnology Techniques, 8, 817-820. 

For continuous perfusion of stirred-tank reactors, several techniques for cell and/or product retention have been developed [2, 110-112]. For cell retention. 

Figure 7.1 Schematics of different cell immobilization techniques using support materials, (a) Surface attachment, (b) Entrapment, (c) Encapsulation, (d) Membrane retention.

We managed to obtain dense and solid thin films of 3d-metal oxides using the techniques of electrochemical deposition from aqueous fluorine-containing electrolytes. The films have been studied as a possible cathode material for secondary cells. The best samples show good cycle retention and acceptable specific capacity in the range of 180 mAh/g. They also feature a plateau of electrochemical potential at approximately 3,5 V, which is acceptable for present industrially produced electrochemical devices. 

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