1. Chapter 6: Plant and Animal Cell Bioreactors

2. Function
Microbial System
Plant Cell System
Bulk mixing
To achieve homogeneity of chemical environment in the presence of nutrient sink and product source terms
To achieve homogeneity of biomass distribution in the presence of sedimentation due to large size of cell aggregates
Oxygen transfer
To meet oxygen supply requirements of the biomass, often limiting in scale up
To meet oxygen requirement of the growing biomass without depleting the concentration of gaseous products below a critical level
Shear
Usually unimportant.
Usually very important due to large size of cells and aggregates.

3. Mammalian Cells

4. Stages in Cell Culture Primary cells Secondary cells
Tissue taken from its original site and transferred to an artificial medium for growth
Requires the recurrent sacrifice of animals
Secondary cells
After the first passage of primary cells
Have a finite number of passages
Continuous or transformed cells
Cells that can be subcultured indefinitely

5. Types of Mammalian Cells
Anchorage Dependent cells
Require surface attachment to grow
They include mostly primary cells and cell lines such as :
-Chinese Hamster Ovary cells (CHO),
Baby Hamster Kidney Cells (BHK) and
Human Fibroblast cells (FS-4)

6. Suspension cells Cells not requiring any surface attachment
Examples are: HeLa cells, hybridoma cells and other tumor cells

7. Some Aspects of Bioreactor Design Design of Bio –Engineering Equipment
Vessel Design (Height : Diameter ratio)
Agitation
Mechanical seal
Stirrer
Inlet air
Aeration
Ports
Exhaust air
Inoculation port
Sampling valve/port
Harvest
Media Addition
Air sterilization

8. Special Considerations for Mammalian Cell Bioreactor
Cells are shear sensitive thus shearing should be minimized
Oxygenation through bubbling may damage cells
Round bottom culture vessel with aspect ratio of 2:1

9. Special Modifications
Aeration and
Mixing

10. Modes of Operation
Batch mode of operation
A well established production method; generally used for vaccines and biopharmaceuticals.
Low yield of product
Batch
The operation modes all lack in the ability to select or differentiate between viable and non-viable cells
Fed-batch mode
High density culture
Longer operation and higher yield
Accumulation of dead cells and debris
Fed-batch
Feed
Continuous mode
High density culture
Product can be harvested continuously
Limited dilution rate
Harvest
Feed
Continuous

11. Perfusion Culture Cell Separation Methods in Perfusion Mode
High density culture
Product can be harvested continuously
High productivity
Dilution rate not limited
Separation of viable and dead cells possible
Harvest
Cell separation
device
Feed
Recycle
Cell Separation Methods in Perfusion Mode
1. Filtration
2. Centrifugation
3. Gravitational settling
4. Immobilisation
All Perfusion strategies must meet the following conditions:
1. Stable operation
2. Easy to scale up
3. Versatility:The process can be applied to any cells and any culture medium
Volume of the production unit is smaller than normally required with batch culture.
Lower investment cost on the bioreactor.

12. Spin filter bioreactors Cell settler for perfusion culture
Perfusion Culture Systems
Spin filter bioreactors
Cell settler for perfusion culture
Centrifugal bioreactor
Tangential flow or crossflow filtration device for perfusion culture
Packed-bed basket perfusion culture
Celligen packed-bed
basket reactor (Wang et al.,1993)

13. Make a comparison of an animal cell bioreactor with a plant cell bioreactor.