Mixing in bioreactor , flow regimes and power requirements

1. XBT 602
PROCESS BIOTECHNOLOGY UPSTREAM
::
Mixing in bioreactor: Flow regimes and power requirement
Submitted By:
Ms.P.Mala Assistant Professor
Department Of Biotechnology
PMIST Vallam
Presented By:
Name: B.NIVEDHA
(121011101423)
ASMA SHAJAHAN
(121011101438)
BRANCH: B.TECH BIOTECHNOLOGY
YEAR: III

2. INTRODUCTION TO MIXING
1.
TYPES OF MIXING AND ITS USES
2.
TYPES OF MIXING EQUIPMENT USED IN BIOREACTOR
3.
FACTORS AFFECTING MIXING
4.
WHAT IS FLOW REGIME AND ITS TYPES?
5.
FACTORS AFFECTING FLOW REGIMES
6.
POWER REQUIREMENTS FOR BIOREACTOR
7.
TABLE OF CONTENTS

3. BIOREACTOR:
A bioreactor is a container where cells, microorganisms, or biological reactions happen in a
controlled environment to make things like medicines, fuels, or other useful products.
MIXING IN BIOREACTOR:
Mixing in the context of bioreactors refers to the process of thoroughly blending and
dispersing the various components within the reactor vessel. In bioreactors, this typically
involves the mixing of nutrients, microorganisms, gases, and other substances necessary
for the growth of cells or microorganisms.
TYPES OF MIXING:
MECHANICAL MIXING
1.
GAS SPARGING
2.
RECIRCULATION
3.
SHEAR MIXINHG
4.

4. Types of Mixing in Bioreactors:
1. Mechanical Mixing:
- Uses mechanical agitation (e.g., impellers, turbines).
- Provides uniform mixing and oxygen transfer.
- Commonly used in stirred-tank bioreactors for microbial fermentation.
2. Gas Sparging:
- Involves bubbling gas through the liquid phase.
- Enhances mass transfer and mixing in airlift bioreactors.
- Used in aerobic processes to provide oxygen to microorganisms.
3. Recirculation:
- Involves recirculating liquid through external loops.
- Enhances mixing and substrate distribution in packed bed bioreactors.
- Useful for immobilized cell cultures and continuous processes.
4. Shear Mixing:
- Utilizes shear forces to mix and disperse components.
- Important for cell disruption and emulsification in some bioreactor processes.
- Used in applications requiring high shear rates, such as cell lysis.

5. Agitators/Stirrers:
These are mechanical devices that rotate inside the bioreactor to mix the contents. They ensure
uniform distribution of nutrients, gases, and cells throughout the culture medium. Agitators come in
various shapes and sizes, and they can have single or multiple blades depending on the
requirements of the bioprocess.
Impellers:
Impellers are rotating components that create fluid motion within the bioreactor vessel. They come in
different designs such as radial, axial, and mixed flow impellers. Radial impellers move fluid outward
from the center, axial impellers move fluid parallel to the axis of rotation, and mixed flow impellers
combine radial and axial flow characteristics. Impellers play a crucial role in promoting mixing,
enhancing mass transfer, and preventing the formation of dead zones within the bioreactor.

6. Gas Spargers:
Gas spargers introduce gases, such as oxygen or carbon dioxide, into the culture medium through
small pores or perforations. The bubbles generated by the sparger enhance gas-liquid mass
transfer and facilitate oxygenation of the culture, which is crucial for aerobic fermentations and cell
culture processes. Gas spargers ensure optimal oxygen levels for cell growth, metabolic activity,
and product formation.
Baffles:
Baffles are stationary plates or protrusions mounted inside the bioreactor vessel to disrupt the
flow pattern and promote turbulence. They help improve mixing efficiency, prevent the formation of
stagnant zones, and enhance heat and mass transfer within the culture medium. Baffles are
particularly useful in large-scale bioreactors and high-viscosity systems to maintain uniform
conditions throughout the bioprocess

7. Magnetic Stirrers:
Magnetic stirrers use a rotating magnetic field to drive a magnetic stir bar placed inside the
bioreactor vessel. They are commonly used in laboratory-scale bioreactors and benchtop setups
for gentle mixing without the need for direct mechanical contact. Magnetic stirrers are suitable for
applications where low shear forces and precise control of mixing speed are required.
Jet Mixers:
Jet mixers utilize high-velocity jets of fluid to induce turbulent mixing within the bioreactor vessel.
They create intense agitation and promote rapid mixing of the culture medium, making them
suitable for applications requiring quick dispersion of powders, dissolution of solids, and
preparation of homogeneous solutions. Jet mixers are commonly used in large-scale bioreactors
and industrial processes.

8. Factors Affecting Mixing in Bioreactors:
1. Agitation Rate:
- Higher agitation rates improve mixing but may lead to increased shear stress on cells.
2. Viscosity of Medium:
- Viscous media require higher agitation rates for effective mixing.
3. Bioreactor Geometry:
- Bioreactor design influences mixing efficiency (e.g., impeller configuration, baffles).
4. Cell Density:
- Higher cell densities can affect mixing by increasing viscosity and altering fluid
dynamics.
5. Gas-Liquid Ratio:
- Optimal gas-liquid ratio is crucial for efficient gas sparging and oxygen transfer.
6. Temperature and pH:
- Temperature and pH variations can affect fluid properties and mixing efficiency.
7. Presence of Foam:
- Foam formation can impede mixing and gas transfer, requiring anti-foaming agents or
foam control strategies.
Effective mixing is essential for maximizing bioreactor performance, ensuring optimal
growth conditions for microorganisms, and achieving desired process outcomes.

9. Uses of Mixing in Bioreactors:
Uniform Distribution:
Ensures even distribution of nutrients, gases, and microorganisms throughout the
bioreactor.
mass transfer:
Enhances mass transfer of substrates and products between phases (e.g., liquid-gas,
liquid-solid).
Homogeneity:
Consistent distribution of nutrients, substrates, and cells throughout the culture.
Oxygen transfer:
Adequate supply of oxygen to aerobic cultures.
Shear control:
Protecting sensitive cells from excessive mechanical stress.
Heat transfer:
Maintaining uniform temperature for optimal growth.

10. 1. Laminar Flow:
Fluid flows smoothly in parallel layers with minimal mixing between layers.
Uses: Common in low Reynolds number systems, such as small-diameter tubes and slow-
moving fluids.
Applications: Microfluidics, small-scale chemical reactions, and certain types of filtration.
2. Transient Flow:
Transitional phase between laminar and turbulent flow regimes, characterized by fluctuating flow
patterns.
Uses: Occurs during the transition from laminar to turbulent flow or vice versa.
Applications: Studying flow instabilities, transitional phenomena in pipes, and mixing processes.
3. Turbulent Flow:
irregular fluid motion with high levels of mixing and eddy formation.
Uses: Common in high Reynolds number systems, where inertia dominates viscous forces.
Applications: Industrial mixing, heat transfer enhancement, and turbulent combustion.
In bioreactors, flow regimes describe how fluids move inside the vessel.
This movement can be smooth (laminar), irregular (turbulent), or somewhere in between (transitional).
FLOW REGIME:

11. Factors Affecting Flow Regimes in Bioreactors
Speed of Mixing, IMPELLERS:
How fast the components are blended affects how fluid moves.
Temperature:
The heat can change how fluids move.
Pressure:
Pressure changes can alter flow patterns.
Rheology of Fluids:
The behavior of fluids under stress affects flow characteristics.
Agitation Mechanism:
Different agitation methods create varied flow patterns.
Fluid Density:
The density of the fluid affects its flow behavior.
Understanding these factors helps control fluid movement inside bioreactors for
efficient mixing and process control.

12. In a bioreactor, power requirements refer to the energy needed to mix substances inside.
POWER:
FACTORS AFFECTING POWER REQUIREMENTS IN BIOREACTOR:
Agitation and Mixing: This refers to the process of stirring the contents of the bioreactor to ensure even
distribution of nutrients and microorganisms. It requires energy to keep things well-mixed.
Aeration and Oxygen Transfer: This involves supplying air or oxygen to the culture to support the growth of
microorganisms. It's like giving them a breath of fresh air and requires power to pump air or oxygen into the
bioreactor.
Temperature Control: This is about keeping the bioreactor at the right temperature for optimal growth and
activity of microorganisms. It requires energy to heat or cool the bioreactor as needed.
Process Monitoring and Control: This involves keeping track of various parameters like temperature, pH, and
oxygen levels, and adjusting them as necessary to maintain optimal conditions for growth. It requires power to
operate sensors and control systems.
Sterilization and Cleaning: This refers to the process of killing any unwanted microorganisms and keeping the
bioreactor clean between batches. It requires energy to heat water or steam for sterilization and to operate
cleaning systems.

13. Which flow regime is characterized by smooth, parallel layers of
fluid with minimal mixing?
a) Turbulent flow
b) Transitional flow
c) Laminar flow
d) Chaotic flow

14. Which of the following factors does NOT influence the power
requirements for mixing in a bioreactor?
a) Fluid viscosity
b) Vessel material
c) Agitation mechanism
d) Desired mixing intensity

15. Which agitation mechanism utilizes rotating magnetic fields to drive
magnetic stir bars within the bioreactor vessel?
a) Aeration
b) Magnetic stirrers
c) Recirculation pumps
d) Impeller agitation

16. In a bioreactor, what fluid property significantly affects the
energy required for mixing?
a) Viscosity
b) Color
c) pH
d) Temperature

17. What is the primary purpose of using impellers in a bioreactor?
a) To measure temperature
b) To create laminar flow
c) To induce mixing
d) To monitor pH levels

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19. THANK YOU