F6 Batch vs fed-batch vs continuous culture, kinetik, utbyten

Question 1

most common bioreactors

Answer 1

stirred tank reactor (STR)
bubble column
air-lift reactor
packed bed reactor

Question 2

bubble column: + och -, use

Answer 2

\+ Simple, cheap, easy to clean 
\+ mixing less energy demanding 
- Foaming a problem 
- Poor mixing 
- High O2 demand 
- Heterogenous flow

Use:
• Bakers yeast, Quorn
• Beer, vinegar
• Waste water treatmen

Question 3

air lift: + och -, use

Answer 3

\+ Simple, cheap, easy to clean 
\+ mixing less energy demanding 
\+ better mixing due to separate up and downstreams 
- Foaming a problem 
- High O2 demand 
- Heterogenous flow

Use: 
• Single cell protein 
• For fragile cells 
• Plant & mammalian cells 
• Waste water treatment

Question 4

packed bed reactors: + och -, use

Answer 4

\+ Simple, cheap 
\+/- requires liquid Recircullation 
\+/- allows biofilm formation 
- Difficult to clean 
- Poor mixing

Use:
• Enzymatic conversions
• Gas fermentation
• Waste water treatment

Question 5

batch cultivation, + och -

Answer 5

+ quick and simple
+ less susceptible to contamination
+ easy to calculate specific growth rate and overall yields
- may lead to substrate inhibition, catabolite repression and overflow metabolism

typical conditions: low product and biomass concentration, high substrate conditions

Question 6

Kontinuerlig odling, + och -

Answer 6

+ Cellernas tillväxthastighet kan styras
+ Typiskt låga substrat- och höga produktkoncentrationer
+ Kan leda till mycket höga produktionshastigheter
‒ Mycket känslig för kontaminationer (fel organism tar över)
‒ Känslig för stabiliteten hos produktionsorganismen, t.ex. förlust av plasmider
‒ Lite krångligare att sätta upp och kan behöva mjuk- och hårdvara för mätning och styrning

Question 7

fed-batch culture, + och -

Answer 7

+ Combines advantages of batch and continuous culture
+ Less susceptible to contamination than continuous culture
+ May lead to very high product and biomass concentration
+ Conditions may be controlled by inlet substrate concentration, inlet flow rate, and volume, but typically the flow rate is used to keep substrate concentration and specific growth rate low
‒ A bit challenging to calculate growth rates and yields
‒ A bit more challenging to set up and requires control software

Question 8

possible set-ups

Answer 8

Chemostat Cascade (kopplade kemostat)
• Two or more reactors in series makes a multistage process in which conditions such as pH, temperature, and medium composition can be varied in each reactor.
→ Advantageous if the reactor conditions required for growth are different from those required for product synthesis
• Used e.g. in the production of recombinant proteins and many metabolites not directly linked with energy metabolism.

Chemostat with Cell Recycle
• With more catalyst present in the vessel, higher rates of substrate utilisation and product formation can be achieved.
• The critical dilution rate for washout is increased, thus allowing greater operating flexibility.
• Commonly used for production
of e.g. ethanol

Question 9

Considerations in design and construction of a bioreactor

Answer 9

• Aseptic operation for many days
• Fulfill containment regulations
• Controlled aeration and agitation
• Low power consumption
• Temperature control
• pH-control
• Sampling fascilities
• Minimized evaporation losses
• Minimal labour in operation, harvesting, cleaning and maintenance
• Suitable for a range of bioprocesses
• Smooth internal surfaces
• Similar geometry of vessels in different scale
• Cheapest material
• Sterilisable and keeping sterility
• Adequate service provisions

Question 10

sterile processes / legislation require containment / non-sterile processes

Answer 10

sterile processes
•Processes that are sensitive to contamination
•High-value products
•Product quality demands

legislation require containment
•Genetically modified microorganisms
•Potentially pathogen microorganisms

non-sterile processes
•Low-value products
•Processes not sensitive to contamination