Millistak+HC AppGd_textC.qxd - Millipore

typical operating conditions). The
addition of the membrane layer further
enhances the retention capability of
the A1HC prefilter, to increase sterile
filter protection dramatically.
In order to achieve this level of
sterile filter capacity, the prefilter must
be highly retentive to small particles
and colloidal materials. The correlation
of sterile filter capacity with the turbidity
of prefilter effluent is shown in
Figure 5. The data show that, to reach
sterile filter capacities in the range of
500 L/m 2 , the prefilter must reduce
fluid turbidity to well below 10 NTU.
0.22 µm Durapore Capacity
(L/m2 @ 20 psid)
700
600
500
400
300
200
100
0
0
Clarified Mammalian Cell Culture
Figure 5. Sterile Filter Capacity as a Function of Feed Turbidity
Depending on the primary clarification
process employed (as shown
in the process schematic in Figure 3
above), secondary clarification will
further reduce turbidity levels by a
factor of 5:1—100:1. Note that
monitoring effluent turbidity can be
a useful guide in determining prefilter
performance, but it should not be used
for actual sterile filter sizing, due to
the complexities of membrane fouling.
Post-Centrifuge
Centrifugation is by far the most
widely practiced method of bulk
cell mass removal for fermentation
10 20 30 40 50
Turbidity (NTU)
1.54 PCV,
60% Viability
Millistak+ HC Filters Application Guide 7