Upstream Bioprocessing Flashcards
What is traditional bioprocessing and it’s products?
Uses cell culture to produce a product
- antibiotics
- vaccines/viruses
- antibodies
- recombinant therapeutic proteins
What’s stem cell bioprocessing and it’s uses?
Cells are the product
Cells and tissue
- Banking/drug screening programs
- larger scale healthcare applications - stem cell therapies
What’s scale up production?
2000l —> 10000l (big tank)
Scaling production up to one large quantity
What’s scale out production?
2000l —> 10000l (5 x 2000l tanks)
Scaling production up to smaller sections of a bigger quantity
What are the advantages and disadvantages of scale up production?
ADV
- is current standard
- we’ll established
- cost effective
- appropriate for allogenic approaches
DIS ADV
- engineering challenges (mixing gradients temp and ph)
- max loss if fails or contaminated
- equipment scale challenges
What are the ADV and DIS ADV of scale out production?
ADV
- allows for parallel runs
- if failure or contaminated minimal loss
- appropriate for autologous approaches
DIS ADV
- Highly laborious unless automated
- less cost effective
What issues do you run into if you have an inefficient scale up production?
Lower economic performance
- lower yield
- lower capacity
- lower product quality
Operational instability
- mechanical instabilities
- genetic instabilities
- variability
Give some examples of planar culture vessels
- t flask
- multilayer plates
- cell factories
- roller bottles
- compact T selecT (automated cell culture platform)
What are the advantages and disadvantages of planar culture vessels?
ADV
- well understood
- reproducible and standardised
- option to be completely automated
DIS ADV
- static systems —> heterogenous culture environment ( not roller bottles)
- poor surface area to volume ratio
- surface limitation and labour intensive
- unreadable for large cell lot sizes
What is a bioreactor?
A vessel in which a bio based process takes place
What is a reactor?
A vessel in which chemical reactions take place
What’s a fermenter ?
A vessel I’m which cells are grown (e.g, bacteria, yeast)
What are the two bioreactor designs
- Submerged —> mechanical, hydraulic or pneumatic bioreactors
- surface
Pneumatic bioreactor : airlift (bubble column) how does it work?
- Aeration and mixing achieved by gas sparging
- less energy and mechanical storing
- satisfactory heat and mass transfer performance
- lower shear - suitable for plant or animal cell culture
- no moving parts - reduce contamination + easy maintenance
- DO and PH control achieved through varying composition and rate of gas flow through column
Give a limitation of a pneumatic bioreactor : airlift ?
Foaming
How does a hydraulic bioreactor : packed (fixed) / fluidised bed work?
- Used for immobilised cells in high density cultures intended for protein production in long term
- cells grow on macro porous beads
- mass transfer is achieved through recirculating the medium in a loop for oxygen enrichment
- low shear rates - simple medium exchange and cell/ product separation
- due to particles in constant motion clogging and channeling avoided
Give an issue with the packed hydraulic bioreactor
Non homogenous cell distribution( only fixed bed) - difficult to harvest
How does a hydraulic bioreactor : hollofibre work ?
- Anchorage- dependant / independent cells
- cartridge of capillary like tubules with perfusable membrane walls
- provides 3D environment for cell grower
- enhanced mass transfer
- used with hepatocytes as an artificial liver
- bioartificial liver
How does a mechanical bioreactor : stirred tank work?
- Mixing achieved through mechanical means using an agitator
- baffles (panels on side of inner of tank) can be used to reduce vortexing
- heating and cooling mantles
- gasing options : headspace or purging
- multiple impellers improving mixing within tall bioreactors
- impellers with different sizes and shapes are used to produce different flow patterns inside the vessel
What are the two stir patterns in stirred tank bioreactors?
Radial ( sideways ovals originating from ends of impeller
Axial ( verticals loops originating from bottom of
Impeller
Describe the 3 types of stirred tank impellers
Rushton
- radial flow
- flat blades
- suitable for high cell density cultures (e.g, bacteria, yeast, some fungi)
Pitched blade
- flat blades 45 deg
- simultaneous axial and radial flows
- suitable for mammalian cell cultures
Marine
- axial flow
- gentle mixing
- suitable for mammalian cells
Describe the Micro carriers characteristic that are used in conjunct with bio reaction
Characteristics :
- small: to max cell culture surface area
- light: to allow easy suspension
- density: slightly higher than medium to allow for faster settling when required
- transparent - to allow easy observation of cell attachment and growth
- appropriate surface chemistry: to promote cell attachment
What are the characteristics of micro carriers?
Micron sized particles made from polymers such as polystyrene, modified dextran, gellan
Come willy available from multiple manufacturers
Different surface chemistries available to determine the physio chemical properties
Suitable for adherent dependant cells
Allow cell attachment and proliferation in suspension cultures
Increased surface area to volume ratio compared to planar systems
What are the three bioreactor operations and their properties?
Batch
- reactants introduced (nutrients + cells) at start of culture
- products recovered at end
FED batch / repeated
- reactants are fed semi regularly
- products recovered at the end
Continuous (perfusion)
- reactors contents mixed and homogenous
- reactants fed in and product removes constantly
- volume of reactor constant
What’s a single use bioreactor and it’s use?
Two types based on medium agitation
1. Stirrers integrated into plastic bags
2. Agitated by rocking motion
- both up to scale of 1000l
- both pre-sterilised
Solid trend: disposable bags for media storage, process development , inoculation, actual bioreactor
What’s are the advantages of a single use bioreactor?
- Quicker turn around times
- No steam sterilisation or cleaning needed
- substantially decreases over timeline and operational complexity
What is scale down?
Scaling production down from a larger tank to a smaller tank
The conditions in the small reactor tank should follow or mimic conditions of the processes in the larger industrial bioreactor
Why is scale down used?
Mainly to troubleshoot existing bio processor
Scale down models used due to limitations on conducting experiments on the pilot scale ( larger tank)
What are the advantages and disadvantage of scale down modes?
ADV
- lower cost due to lower quantities of raw materials req
- can test conditions not possible with the process equipment that can cause damage ( temp, pressure)
DISADV
- difficult to mimic the conditions at process scale
- is an incomplete representation of more complex, expensive and physically larger system
What factors help decide the appropriate scale down model?
Many scale down criteria used
- suspending : tip speed : interferior with more scale
- micro mixing : energy dissipation : equal between scales
- macro mixing : mixing time : interferior with inc scale
- mass transfer : comparable
- shear force : comparable
Choice depends on project and cell line characteristics
Acceptance criteria
- performance scale down mode should match the large scale product and process
- outputs of manufacture scale process and sdm need to be compared
What factors make an ideal scale down model?
- faithful representation of process equipment
- product : data
- universally used
- low volume
- rapid testing
- rapid optimisation
- parallel investigation with setup and run time efforts that remain nearly independent of number of bioreactors
What are the advantages of microfluidics ?
- high oxygen transfer rates without bubbles
- online optical density measurement
- online growth rate estimation
- measurements do not perturb fermentation
- minimal mechanical parts
- compact, bench scale instrument
What are the ambr15 microbioreactor properties?
Ambr15 (Sartorius, TAP)
- disposable microbioreactor
- disposable sensor
- working volume 10-15ml
- automated workstation
- 12 vessel capacity
- closed loop control of PH and DO with independent control of o2 and co2 fro each vessel
What are the properties of the simcell (thermofisher) microbioreactor?
- 6 micro bioreactors per array
- working volume 700 micro litres
- fluid ports and channels for inoculation feeds ph adjustment and sampling
- culture monitoring of biomass (OD) ph , DO (immobilised sensors)
- incubator : one to five per system T co2 o2 and agitation control
Sensing module
- total biomass by OD
- pH by immobilised sensors
- DO by immobilised sensors
Why use ultra scale down?
- Predicts how full scale operation performs
- rapid acquisition of data using small amounts of material
- early insight into processing issues
What is a seed train?
A sequence of bioreactor inoculations to achieve scale
