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Principles of Biochemical
Engineering
ENCH 535 Winter 2016
Bioreactor Scale Up
March 28, 2016
Scale up of bioreactors
Reactor dimension
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Choosing the reactor type
Bioreactors
Submerged
cultures
Stirred tank
Airlift
Immobilized
cultures
Bubble
columns
Reactor types
Packed bed
Fluidized
beds
Airlift
Stirred tank
Figures source: http://en.wikipedia.org/wiki/File:Bioreactor_principle.svg
http://www2.hawaii.edu/~wsu/bioreactor/sld004.htm
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Reactor types
Figures source:
Bubble-Column
http://en.wikipedia.org/wiki/File:Bubble_column.svg
http://www.algaeindustrymagazine.com/algae-scale-up-bioreactors-from-biovantage-resources-inc/
Reactor types
Air-lift
Figures source: http://www.babonline.org/bab/045/0001/bab0450001f03.htm?resolution=HIGH
http://whs.inha.ac.kr/~kimdi/lab1.html
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Packed Bed Reactors
Hollow Fiber Cell Bioreactor
Fluidized Bed Reactors
gas
Effluent
ORP, pH
probes
Recirculation
pump
Water-jacketed
glass reactor
carrier
Glass
beads
wastewater
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Conceptual steps in scale-up
Scale-up issues
A scale-up problem is something that we do not see in the
small-scale experiment and are surprised and disappointed
to find in the large scale process
Heat transfer
Mass transfer (oxygen)
Power input
Foaming
Sterility
Product quality
By-product formation
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Scale-Up Parameters
Geometry
Height to Diameter Ratio is held constant
Called aspect ratio
Scale-Up Parameters
Agitation-based parameters
Mixing time
Power input per Volume (P/V)
Tip Speed
Gassing-based parameters
Vessel Volumes per Minute (VVM)
Superficial Gas Velocity (Vs)
NOTE: Cannot keep all parameters constant during scale
up because they scale by different values
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Parameter
Definition
Scale-Up Factor
Importance
N2=N1(D1/D2)1/4
Mixing time
Power input per
volume (P/V)
Amount of time it takes the
bioreactor to create a
homogeneous environment
Amount of power
transferred to a volume of
cell culture through the
agitator shaft and impellers
N2 agitation speed in scale-up
N1 agitation speed in scale-down
D1 impeller diameter of scale -down
D2 impeller diameter of scale-up
Cells cannot handle a lot of
power introduced into the
culture media as it can cause
small eddies that will shear the
fragile cell membranes
P/V N3/D2
P- power supplied
V- Volume of Bioreactor
N- Agitation Speed
D- Impeller Diameter
N2=N1(D1/D2)
Tip speed
Related to the shear rate
produced from the
impellers moving through
the cell culture media
Superficial gas
velocity (Vs)
Volume of gas per crosssectional area of the vessel.
Vessel Volume
per minute (vvm)
Volume of gas flow (usually
measured in slpm,
standard liters per minute)
per bioreactor volume per
minute.
Need to ensure that the
materials are well-mixed in a
timely manner
N2 agitation speed in scale-up
N1 agitation speed in scale-down
D1 impeller diameter of scale -down
D2 impeller diameter of scale-up
Vs = Qgas/Av
Vs- superficial gas velocity
Qgas- gas volumetric flow rate
Av- inside cross-sectional area of
vessel
Volume of Gas Flow/ ( time x
Reactor volume)
High shear rates can cause the
cell membrane to tear and the
cells to die.
If scale-up based on constant
tip speed is attempted, P/V and
mixing time will decrease
increasing Vs causes an
increase in foam generation
A decrease in P/V
An increase in oxygen transfer
Necessary to ensure that enough
oxygen will be supplied to the
cells
Interdependence of Parameters on Scale-Up
Scale-up criterion
Symbol Small
scale (80L)
P0 /V
Large scale (10000 L)
N
N Di
Re
Energy input
P0
1.0
125
3125
25
0.2
Energy input/volume
P0/V
1.0
1.0
25
0.2
0.0016
Impeller rotation
1.0
0.34
1.0
0.2
0.04
Impeller diameter
Di
1.0
5.0
5.0
5.0
5.0
Pump rate of impeller
1.0
42.5
125
25
5.0
Pump rate of
impeller/volume
Q/V
1.0
0.34
1.0
0.2
0.04
Impeller speed (max
shearing rate)
N Di
1.0
1.7
5.0
1.0
0.2
Reynolds number
NDi2/
1.0
8.5
25.0
5.0
1.0
Table source:
Schuler-Kargi, Bioprocess Engineering, Basic Concepts, Prentice-Hall, 2002
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Scale-up Strategies
Rules of thumb:
Constant specific power input
Constant kLa
Constant impeller tip speed
Constant DO
Trial and error:
only for small scale-ups (one order of magnitude)
Expensive
Rigorous simulation:
Not always possible
Experimental data needed for validation
Rigorous Simulation: CFD
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CFD
Definition: Numerical solution (computer simulation) of differential equations
describing fluid flow, heat, mass, and momentum transfer, chemical reactions.
Advantages
Disadvantages
Able to develop a virtual model of your
system of study
Need CAD experience to develop the
model
Perform virtual experiments in the
model that are difficult to perform in
the actual system
Need the meshing knowledge
Allows one to evaluate many changes,
configurations, and set-up in minimal
time
Need fluid dynamics experience
develop the equations for what you are
wanting to model
Gain a picture of the 3D space that is
difficult to quantify experimentally
Need a lot of computing capacity
Heat Transfer
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Mixing
Mixing is the achievement of uniformity
Purpose:
Blending: substrate, pH control
Suspending: solid particles, immobilized cells
Dispersing: two liquid phases, aeration
Agitated tanks - Impellers
Rushton turbine
Marine propeller
Lightnin A310
Pitched bladed turbine
Figures source: http://www.postmixing.com/
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Quantifying mixing power
Oxygen transfer coefficient
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Foaming
Foam is a natural byproduct mostly protein
bubbles but some lipids
Foam will block and wet filters causing pressure
back-up and contamination
Foam must be controlled by chemical dispersing
agents (antifoams) or mechanically broken
Maintaining 75% volume capacity of reactor
allows for foam to be retained within the vessel
Sterility
Sterilization in place (SIP)
cleaning of reactor and bed
without dismantling reactor or
feed tubes
Pressurized steam is used for inplace sterilization of probes,
valves and seals
All crooks, crevices and surfaces
are potential contaminants and
must be sterilized
Sterilization must be verified and
validated
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