For larger quantities, powder formulations may be considered.

Following the protocol of the provider, a liquid formulation can

then be generated by the addition of cell culture grade water.

Generally, media and feeds were designed simultaneously to enable

the cellular metabolism to secrete high quantities of recombinant

protein. Usually, such medium feed combinations are provided

with basic protocols describing cultivation conditions and timing

of feed addition, allowing to quickly obtain reasonable results.

Media and feeds can have a major impact on the performance of a

specific cell population with regard to doubling time, production

level, and product quality [14]. It may thus be advisable to perform

Fig. 1 (a) Sampling port—allows for the removal of cells and culture liquid for

analysis using a syringe. The risk of contamination can be reduced by spraying

the port with ethanol before and after sampling. (b) Filters attached to gas inlet

and exhaust. Care needs to be taken to prevent moisture from accumulating on

the filters which would lead to clogging. (c) Headplate with connections for liquid

addition and ports for probe insertion. Missing of damaged O-rings on the probes

result in a high contamination risk. (d) Impeller—various designs are available

resulting in different mixing characteristics and shear stress to the cells. Shown

here: Rushton type impeller more commonly used for microbial applications. (e)

Sparger—allows for efficient transfer of gases to the cell culture liquid. Different

designs result in different bubbles sizes greatly influencing gas transfer and

shear stress. Shown here: macrosparger

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Ange´ lique Schmid et al.