Upstream Bioprocessing Flashcards
What are the products of traditional bioprocessing?
- Antibiotics
- Vaccines / viruses
- Antibodies
- Recombinant therapeutic proteins (i.e. MAb) (Global market worth £30 billion/year)
What are the applications for (Stem) Cell bioprocessing?
- Cells and Tissues
- Banking/Drug screening programmes
- Larger scale healthcare applications →Stem cell therapies (potential to cure diseases, not just to treat/address symptoms)
Describe bioprocessing complexity
Draw a diagtam of therapeutic agent production
Draw a table of cell requirements
Describe the INDUSTRIAL SCALE meaning for biotherapeutics
- >10,000 Litres – Monoclonal antibodies (MAbs) and proteins
- 2,000 Litres – Viral vaccines
- 50 Litres – Human mesenchymal stem cells for therapies
(Lawson et al, 2017)
Scaled out production
Scaled Up production
Advantages of scale-up
- Is the current industrial standard.
- It is well established.
- Cost effective.
- Appropriate for Allogeneic approaches
Advantages of scale-out
- Allows for parallel runs.
- In case of contamination or failure, only minimal loss.
- Appropriate for Autologous approaches.
Disadvantages of Scale up
- Many engineering challenges (e.g. mixing, gradients, temperature and pH maintenance).
- In case of contamination or failure, maximal loss.
- Equipment scale challenges.
Disadvantages of scale-out
- Highly laborious unless automation is used.
- Less cost effective.
What are the biological and engeineering considerations for scaling up production?
- Scale-up is usually the final step of any R&D programme
- Biologists usually don’t fully understand the challenges of a scalable process
- Engineers don’t always understand the biology
- Engineers don’t get involved soon enough
- Scaling up a bioprocess requires important engineering aspects that have to be considered early in the process => DETRIMENTAL effect on the overall manufacturing process
Inefficient scale up: Lower economic performance
- Lower yield
- Lower capacity
- Lower product quality
Inefficient scale up: Operational instability
- Mechanical instabilities
- Genetic instability
- Variability
Name some planar culture vessels
- T-flasks
- Multilayer plates
- Cell factoreies
- Roller bottlesCompacT SelectT– automated cell culture platform
Draw a diagram of bioreactor designs
Explain how a Pneumatic bioreactor works: Airlift (bubble column)
- Aeration and mixing is achieved by gas sparging
- Less energy than mechanical stirring
- Satisfactory heat and mass transfer performance
- Low shear→ suitable for plant or animal cell culture
- Absence of any moving parts →reduced contamination and easy maintenance
- DO and pH control achieved by varying the composition and the rate of the gas flow through the column
- Challenge: foaming
Explain how a Hydraulic bioreactor works: Packed (fixed) /fluidised bed
- Used for immobilised cells in high density cultures intended for protein production in long term cultures
- Cells grow on macro-porous beads (e.g. glass, ceramic)
- Mass transfer is achieved by recirculating the medium in a loop for oxygen enrichment
- Low shear rates, simple medium exchange and cell /product separation
- As particles are in constant motion, channelling and clogging is avoided (only Fluidised Bed)
- Non-homogeneous cell distribution (only Fixed Bed), difficult cell harvest.
Explain how a Hydraulic bioreactor works: Hollowfibre
- Anchorage-dependent / independent cells
- Cartridge of capillary-like tubules with perfusable membrane walls
- Provides a 3D environment for cell growth
- Enhanced mass transfer
- Used with hepatocytes as an artificial liver (Bio-Artificial Liver-BAL)
- Bio-Artificial Kidney – BAK
Explain mechanical bioreactor: Stirred Tank (STR)
- Mixing is achieved by mechanical means using an agitator (e.g. impeller)
- Baffles can be used to reduce vortexing
- Relatively high input of energy
- Heating/cooling mantles
- Gasing options: headspace or purging
- Multiple impellers improve mixing within tall bioreactors
- Impellers with different sizes and shapes are used to produce different flow patterns inside the vessel
Mixing in STR: flow patterns
STR: impellers
Rushton
- Radial flow
- Flat blades
- Suitable for high cell density cultures (e.g. bacteria, yeast, some fungi)
STR: impellers
Pitched-blade
- Flat blades, 45°
- Simultaneous axial and radial flow
- Suitable for mammalian cell cultures
STR: impellers
Marine
- Axial flow
- Gentle mixing
- Suitable for mammalian cells
What are the characteristics of microcarriers?
Small: to maximize cell culture surface area (high area-to-volume ratio)
Light: to allow easy suspension in culture medium
Density: slightly higher than medium to allow for fast settling when required
Transparent: to allow easy observation of cell attachment and growth
Appropriate surface chemistry: to promote cell attachment
Name some scalable culture systems - microcarriers
- Plastic (polystyrene)
- Cytodex 1 (dextran)
- Collagen
- Cytopore (gelatin)
- Hillex II (modifies polystyrene)
- NUNC 2D MiroHex (polystyrene)
Bioreactor operation modes: Batch
- Reactants (nutrients and cells) are introduced at the start of the culture
- Products are recovered at the end (batch wise)
Bioreactor operation modes: FED BATCH / REPEATED
- Reactants are fed semi-regularly (semi-continuously
- Products are recovered at the end (batch wise)
Bioreactor operation modes: CONTINUOUS (PERFUSION):
- Reactor contents is mixed and homogeneous
- Reactants are fed in and product is removed constantly
- Volume of the reactor is constant
