Bioreactor Systems

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Bioreactor Systems
Ka-Yiu San
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A Fermenter / Bioreactor And Its Parts
by Genentech, Corporate Communication
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1500L-Scale Bioreactors(courtesy of Tanox )
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Bioreactor Advantages

• Controlled environment
• Mixing
• pH
• Dissolved oxygen
• Temperature

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pH probe

1. Steam sterilizable
2. Combination electrode

Dissolved oxygen probe

• Two major types
• Galvanic
• Polargraphic

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Galvanic and Polargraphic Probes
Cathode 0.5 O2 H2O 2e- ?
2OH-
Pt
Anode (galvanic) Pb ? Pb2
2e-
Anode (polargraphic) Ag Cl- ?
AgCl e-
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Mode Batch Fed-batch Continuous (e.g.. chemostat)
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Batch
Time
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Fresh nutrient
volume
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Continuous
Fresh nutrient
cell Spent broth
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Recombinant processes
- An engineering perspective
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Cloning for rProtein production
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Cloning vector properties

• Origin
• Size of backbone
• Well characterized
• Selective marker
• Genetic marker
• Unique restriction sites

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• Some factors that affect gene expression
• Gene dosage (copy number)
• Plasmid stability (structural and segregational)
• 3. Transcription
• - Promoter and terminator sequences
• (promoter strength, inducible - leakage)
• - Regulatory genes and sequences
• 4. Translation
• - Ribosome binding site (Shine-Delgarno
  sequence) - Codon optimization to match host's
  codon bias
• 5. Final location of gene product
• - Cytoplasmic or extracellular (secreted
  out of cell)

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• Some factors that affect gene expression (contd)
• 6. Protein stability
• - Degradation by host proteases -
  Formation of insoluble aggregates
• Strain
• Process consideration
• - Medium
• - Temperature (growth vs. production)
• - Dissolved oxygen
• - Induction timing
• - Feeding profile (fed-batch)
• - waste product accumulation

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Cell Culture
- An engineering perspective
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Outline

• Examples

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• Two major classes
• serum supplemented
• serum-free (or low serum)

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Environment considerations
- nutrient supply
- mixing
- oxygen supply
- pH
- carbon dioxide
- temperature
- waste accumulation
- lactate
- ammonia
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Relative specific growth rate
Kolmogorov length scale (microns)
Relative net growth rate versus Kolmogorov eddy
length scale for FS-4 cultures with 0.2 g/l
microcarriers
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Typical cell growth on microcarriers
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Typical cell growth on microcarriers
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Perfusion system - to provide fresh nutrient - to
remove waste (especially toxic byproducts -
mechanical signal
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Questions?