measurement of dissolved glucose levels should be at hand.

This can for example be performed with an over-the-counter

glucose meter. Lactate, ammonia, and other metabolites such

as glutamate and glutamine could be of interest to be measured

to further optimize the feeding strategy based on these com-

pounds (to keep their concentration low or the supply enough

in case they are important for the culture).

3. Tubing will be required to connect bottles or other containers

with feeds, antifoam, and glucose as well as to transfer the cells

for the inoculation. Usually weldable tubing (thermoplastic

elastomer tubing) is not suitable for pumping operations

which should be done using silicone or bioprene. Silicon tub-

ing however cannot be welded so adaptors are required to

connect to the weldable tubing. Bioprene could be welded

but is expensive, especially since lines to connect the bioreactor

to the vessels containing, e.g., feeds passing through the pump

can be quite long. Use of another weldable tubing will reduce

global cost. Especially single-use and/or larger bioreactors that

cannot easily be moved require significant planning before

operations in order to establish all connections in a sterile and

efficient manner.

4. Tubing welders allow to quickly establish sterile connections to

the bioreactors used for addition and removal of media and

cells. Their use is applicable to connect vessel which required to

be connected after bioreactor preparation, either because they

could not be sterilized with the bioreactor (sensitive to heat),

because the line will be used for another purpose first or

because the liquid to add needs to be connected at a defined

time (inoculum, material sensitive to light or heat). Alterna-

tively, tubing assemblies with sterile single-use connectors are

available from a number of suppliers.

Otherwise and especially when glass bioreactors are used,

connections can be established prior to addition of the media

under non-sterile conditions followed by autoclaving. Contain-

ers with heat sensitive components like media can then be

attached inside a lamina flow hood. Connection of tubing

assemblies under the lamina flow hood could be done at the

time of bioreactor preparation.

5. Not all media and feeds are compatible. In particular, several

manufacturers provide two separate feeds that precipitate if

mixed undiluted due to the pH required to solubilize the

ingredients at high concentrations. Thus, care has to be taken

to avoid mixing of incompatible components for example if

only a single feed line is used.

6. Often, the amount of glucose added is based on the difference

between the

remaining glucose

level in the bioreactor

Benchtop Bioreactors in Mammalian Cell Culture: Overview and Guidelines

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