This presentation explores bioprocessing filtration best practices, including design and scale up methods. You will learn: • What is filtration? • Filter capacity and fouling models • Filter sizing approaches • Scale up considerations To learn more about this topic or collaborate with our technical experts, schedule a remote visit at our M Lab™ Collaboration Centers: www.emdmillipore.com/remotevisit

1. Merck KGaA
Darmstadt, Germany
Marine Maszelin, EMEA Process Development Scientist
Partner4Biotech Genopole, June 18, 2020
Design and Scale Up
Normal Flow
Filtration

2. 01
02
03
04
Agenda
2
What is Filtration?
Filter Capacity and Fouling Models
Sizing Approach
Scale Up Considerations

3. 3
Tangential Flow FiltrationNormal Flow Filtration
What is Filtration?
Two different approaches
Pressure driven separation process that uses (membrane) filters to separate components
in a liquid (or suspension) based on their size
Two types of filtration
Filtratefluxrate
Volume filtered
Filtratefluxrate
Volume filtered

4. 4
Normal Flow Filtration (NFF)
1 2
3
4
Cartridge or
“Dead-ended” Filtration
Flow is perpendicular
to the filter media
All fluid passes
through the media
Particles are retained
in/on filter
Examples:
 Clarification, prefiltration
 Bioburden reduction, sterilizing filtration, viral clearance filtration

5. 5
Where are the Normal Flow Filters in my BioPharm Process?
Cell culture
supplements, Media
prep and Mixing
Pre-filtration Bioburden reduction
Bioburden reduction
Bioburden
reduction Bioburden reduction,
aggregate removal,
diafiltration…
Bioreactor
Clarification
Protein A
Chrom
Virus inactivationCation exchange
Chrom
Anion exchange
Chrom
Virus filtration Concentration
Diafiltration
Final Formulation Sterile filtration Final Fill

6. What happens when a filter blocks?
Flow rate goes down
- May drop below the required flow rate (i.e. filling machine)
Pressure goes up
- May exceed the system differential pressure capabilities
- Cartridge or tubing / fittings
Particles may "bleed" through the filter
- Contaminates / blocks the downstream cartridges
The cost of filtration changes
- Time, product & cartridge cost included
- System should be shut down & cartridge(s) changed
6
1
2
3
4

7. 01
02
03
04
Agenda
7
What is Filtration?
Filter Capacity and Fouling Models
Sizing Approach
Scale Up Considerations

8. During filtration particles capture could result in:
 Filter plugging (increase resistance to flow)
 Saturation of filter membrane
 The two events can affect process
Filtration should be stopped before:
 A defined time frame
 Reaching a certain filtrate flow
 Impacting product yield
 Contaminants passage
Filter capacity is the volume filtered just before this point
 It depends on filter retention mechanisms
How to Define Filter Capacity?

9.  Size exclusion
 Sieving (surface)
 Capture (depth)
 Adsorption
 Attraction forces
between particles and media
 Electrostatic / Hydrophobic interactions
/ Zeta potential
 Size independent
 Mechanism related to
 Particle type
 Filter media and structure
Particle Retention Modes
9

10. DEPTH FILTERS
High capacity
€
SURFACE FILTER / PRE-FILTER
Good efficiency
€ €
MEMBRANE FILTER
Total security
€ € €
Three Main Filter Families

11. 11
 Porous layer of tough particles on the filter
 Liquid go through the filtration cake
− Filtration cake thickness increase is directly proportional
to filter upstream pressure
 Common for primary clarification or coarse filtration
− Example: resin, fines, diatomaceous earth filtration…
Cake Filtration

12. 12
 Impermeable layer of deformable particles on the
filter
 Fluid cannot go through the filter
− Quick and brutal increase of filter upstream pressure
 Common when no pre-filter is used (or insufficient),
or when deformable particles are slightly bigger
than filter pore sizes
− Examples: colloid fluids (cell cultures, serum…)
Complete Pore Blocking

13. 13
 Progressive accumulation of particles in the filter
− Tough or deformable particles
 Filtrate flux gradually decays
− Or slight increase of filter upstream pressure
 The most common fouling model for biopharmaceutical fluids
− Surface filters or membrane filters
Gradual Fouling Model

14. 14
Fouling Models
Complete
Cake
Gradual
DP
Time
Cake
Gradual
 Gradual pore plugging
 Complete pore plugging
 Cake filtration

15. Choose a Sizing Method
Pmax™ method
Testtype
Adsorption Complete
pore
plugging
Cake Gradual
pore
plugging
Constant
pressure
Constant
flow
Vmax™
method
Tmax
method
Retention / Fouling mechanism
Turbidity increases
during filtration
Pressure drop increases during
filtration
Flux decay increases during filtration
15

16. 01
02
03
04
Agenda
16
What is Filtration?
Filter Capacity and Fouling Models
Sizing Approach
Scale Up Considerations

17. 17
 Sizing tool for surface and membrane filters
 Fast test under constant pressure
 Based on gradual pore fouling model
 Particles are smaller than filter pore size and gradually plugged the filter
 Monitoring of filtrate flux decay during the test
 Vmax™ value is the theoretical maximum amount of product that can be filtered before the
membrane is totally plugged (i.e. the filtration flow rate becomes null)
 Happens when t→ 
What is Vmax™ Methodology?
time (min.)
Traditional Flow Decay
0
2
4
6
8
10
12
0 10 20 30 40 50 60
t/V(min/L)
Vmax
Publication: ”Forrest Badmington, Randy Wilkins, Michael Payne, and Ephraim S. Honig. Vmax testing for Practical
Microfiltration Train Scale-Up in Biopharmaceutical Processing, Pharmaceutical Technology, September 1995, p64-76.”

18. Vmax™ Method: Test Procedure
Constant pressure
filtration flow rate
decreases as
pores are blocked
t/(V/Area)
t
1/Qi
1/Vmax™
Qi
Volume per area
V/Area
Time, t
≈
∞
Vmax™
Compressed
gas
Test
filter
Pressure
vessel
t / (V/Area) = At + B
B = intercept = 1/Qi
A= slope=1/Vmax™
After bleeding the filter, the product is pushed at constant pressure
through the filter.
Data are collected during 10-30 min:
 Cumulated volume of filtrate (V)
 Time (t)
18

19. Vmax™ Method: Capacity Range
>5000 L/m² High capacity / low fouling fluid
ex: buffers
250-5000 L/m² Moderate capacity / moderately fouling
fluid
ex: most solutions after
adequate prefiltration
<250 L/m² Low capacity / very fouling fluid
ex: unfiltered serum
19

20. Vmax™ Method: Sizing Scenarios
max
min
V
V
A B
=
Case 1. Only VB (Batch Volume) is known
Bi
BB
tJ
V
V
V
A

+=
max
min
Case 2. VB (Batch Volume) and tB (Batch time) are known
Case 3. VB (Batch Volume), tB (Batch time) & Jmin (minimum flow) are known
Iterative calculation (trial/error)
Case 4. Sizing by flux (non fouling fluids)
meanb
b
Jt
V
A
x
min =
minmaxmin
min
1
AV
V
AJ
J B
i 
=

−
20

21. Vmax™ Method
Advantages
 Predictive method: no need to test until max capacity is reached
− Quick testing (15-30 min; buffers Kbuf better option)
− Low fluid volume required
− Allows for multiple testing (screening method)
 Powerful analysis tool
− 2 parameters for sizing (permeability + Vmax™)
− 4 scenarios for sizing
Limits
 Only applicable to gradual pore plugging
− Not applicable to depth filters
21

22. 22
 Can be used for all filter types (depth, surface and membrane) but specifically used for
depth filters
 Non-predictive experiment
 Based on real filter capacity
 Can be used for all the fouling models
 Monitoring of filter upstream pressure increase (Pmax™) and/or filtrate trubidity (Tmax™) during
the experiments
 Pmax™/Tmax™ is the amount of product that can be filtered before a defined upstream
pressure or a defined filtrate turbidity is reached
What is Pmax™/Tmax™ Methodology?

23. Constant flow experiment: Pmax™ or/and Tmax™
- Constant residence time (adsorption)
- Procedure
Equipment: pump, pressure gauge, balance
Set-up:
Data: pressure and feed flow monitoring, measure of contaminants passage (turbidity, OD550nm or
OD280nm)
Pmax™/Tmax™ : Testing Depth Filters
23

24. Pmax™ /Tmax™ methodology
Filter capacity is reached when:
- Trial pressure = pressure endpoint (Pmax™)
OR
- Filtrate turbidity breakthrough is observed (Tmax™)
Turbidity(NTU)
Pressure(psi)
Filtrate volume (L/m²)
Capacitiy at
small-scale
Sizing
Manufacturing
parameters
24

25. Pmax™ Method: Capacity Range
> >350 L/m2 High capacity
ex: supernatant CHO cells after
centrifug.
100 - 350 L/m2 Moderate capacity
ex: permeate after TFF
microfiltration
<<100 L/m2 Low capacity
ex: high density cell culture
25

26. Pmax™/Tmax™
Advantages
 Applicable independently from retention/ plugging mechanism
− Analysis of empirical data
− No mathematical model
Limits
 No predictive model: test needs to be performed until max capacity
− Need for sufficient product volume
− Test time can be long : 2-6h (→ several parallel filtrations)
26

27. Rule of thumb is 1.3-1.5X safety factor, but…
It depends on:
 Quantity and quality of data
 Expected variability of feed solution
 Expected variability of filter
 Available filter sizes
 Scale-up factor
Sizing and Safety Factor
Minimal
area
Process
area
minA
A
factorSafety
process
=
27
Publication: ”Herb Lutz. Rationally defined safety factors for filter sizing, Journal of Membrane Science, Volume 341 (2009), p268–278.”

28. 01
02
03
04
Agenda
28
What is Filtration?
Filter Capacity and Fouling Models
Sizing Approach
Scale Up Considerations

29. 29
Filtration Train Development Strategy
3. Simulation trials
Objective: sizing
confirmation with process
conditions
2. Screening trials
Objective: identify the best
filtration train and size it
quickly
1. Test filter
identification
Filter to be evaluated
Depth filters:
Tests Pmax™/Tmax™
Final process with
pump:
Pmax™ mode
simulation
Surface/membrane
filters:
Tests Vmax™
Final process under
constant pressure:
Vmax™ mode
simulation

30.  Filters are tested
separately (not as a
train).
 Feedstock quality is
uniform during
filtration.
 Pressure is uniform
(Vmax™ test).
During screening
tests…
 Check filter performances
(capacity and filtrate
quality) in process
operating final conditions.
 Check Safety Factor for
sizing (adjust if needed).
 Prepare Scale Up-Down
(max factor 100x).
 Generate filtrate for DSP
steps design.
Simulation
trials
 Filters are ‘in-line’
(filtration train).
 Feedstock quality varies
if upstream filters foul.
 Pressure repartition can
vary for each filtration
step.
 Flows and feeding
methods
(pump/pressure) can
differ from those applied
during testing.
During
Manufacturing…
Objectives
30

31. How to Minimize Filtration Problems
Use low initial differential pressure
− ~1-2 psid or ~0.1 bar
Monitor & change on differential
pressure
 Biological fluids
− Depth Filters : 10 - 15 psid (0.7-1
bar)
− Surface Filters & Membrane Filters :
30 - 50 psid (2-3.3 bar)
− When filter specification is exceeded
Ensure adequate pressure from
pressure source (pump / pressure vessel)
31
1
2
3

32. Normal Flow Filtration: Design and Scale up
Take away
NFF Design
and Scale-
up |
Genopole |
18.06.2019 32
Process
Requirements
Screening
Bench Scale
Process Simulation
Bench/Pilot Scale
Implementation
Large Scale
Scale Down
Strategy Troubleshooting

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