ThermoFisherScientific_Jan2021_ADeepDiveInto - 21

A Deep Dive into Perfusion Media for Bioprocessing Applications

Know Your Test Model
Once clear design goals are established, the next step
is to define a test setup. You want the testing to give
you results that are meaningful to your process goals
and make sure the equipment and materials used
don't become accidental limiting factors. The following questions need to be considered before you run
your test model:
* How long will you run your process?
* How much oxygen transfer can you support?
* What is your target scale-up and what additional
restrictions will this cause, such as how much shear
will be generated?

Ideally, your test setup allows the systematic evaluation of critical parameters to optimize cell viability and
productivity. And, it will help identify the parameters
that require scaling and how much flexibility exists.
For example, there are multiple approaches to scaling
agitation (Table 1), so it is important to know what
your process limits are. When combined with your
product quality needs, these limits should establish
control boundaries for your run, which are meaningful
with respect to how you plan to operate the process.
This will also help avoid your results being limited by
an unplanned or, worse, unnoticed factor in your test
model. Additionally, it will help reduce risk when
scaling up the process.
Table 1. Common agitation scaling parameters in a 3 L benchscale stirred-tank reactor at increasing rpm. Typical animal
suspension cell culture agitation power (W/m3) is highlighted
in blue. Progressive comparative minimum tip speeds are
highlighted in orange and red with process scale up to
2,000 L, and Kolmogorov eddy length common targets using
microcarrier beads are highlighted in green.

Agitation scaling parameters

Ideally, your test setup allows the
systematic evaluation of critical
parameters to optimize cell
viability and productivity.

Reactor
speed
(rpm)

Agitation
power (W/
m3)

Tip speed
(m/sec)

Pow num

Kolmogorov
length (µm)

0.42

0.16

1.99

91.345

1.02

0.22

1.89

73.326

200

14.99

0.59

1.47

37.417

239

25.26

0.70

1.45

32.841

292

45.07

0.86

1.42

28.416

348

75.22

1.02

1.40

25.001

389

105.06

1.14

1.40

22.997

443

155.17

1.30

1.40

20.861

486

204.88

1.43

1.40

19.461

555

305.11

1.63

1.40

17.617

610

405.11

1.79

1.40

16.411

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