1. Design of Fermenter
Lecture

2. Basic functions of a fermenter for microbial or animal cell culture
The vessel – capable of being operated aseptically for a number of days
Adequate aeration and agitation – meet requirements of micro-organisms
Power consumption should be as low as possible
Temperature control and pH should be provided
Vessel should be reliable in long-term operation and meet requirements of containment regulations. Aeration and agitations should not cause harm to the microorganisms

3. Basic functions of a fermenter for microbial or animal cell culture
Sampling facilities should be provided
Evaporation losses from fermenter should not be excessive
Minimal use of labor in operation, harvesting, cleaning and maintenance
Should have internal smooth surfaces
Similar geometry of both smaller and larger vessels
Similar geometry of vessels in plants to facilitate scale up

4. Aseptic operation and containment
Aseptic operation involves protection against contamination
Containment involves prevention of escape of viable cells from a fermenter or downstream equipment
Lowest level hazard micro-organisms – require GILSP
Good industrial large scale practices except some organism used in bacterial and viral vaccine production. Lowest level mo can be genetically or non-genetically engineered organisms.

5. Achievement and maintenance of aseptic conditions
Sterilization of fermenter
Sterilization of air supply and exhaust gas
Aeration and agitation
Addition of inoculum, nutrients and other supplements
Sampling
Foam control
Monitoring and control of various parameters

6. Construction materials - Body
Possible to use glass and/or stainless steel
Glass vessel with a round or flat bottom and a top flanged carrying plate – autoclave
Largest possible diameter-60cm
Glass is useful because it gives smooth surfaces, which is non-toxic, corrosion proof and it is usually easy to examine interior of vessel

7. Construction materials - Body
A glass cylinder with stainless-steel top and bottom plates
More expensive (50%)
Pilot-scale and industrial scale – stainless steel
Chromium % develops an effective film . The inclusion of nickel in high percent chromium steel enhances their resistance and improves engineering properties. The presence of Mo improves resistance of stainless steels to solutions of halogen salts and pitting by chloride ions in brine or sea water. Corrosion resistance can also be improved by tungsten, silicone and other elements

8. Construction materials - Body
Aseptic seal – made between glass and glass, glass and metal or metal and metal joints between fermenter vessel and a detachable top or base plate
Compressible gasket, a lip seal or an ‘O’ring
With glass and metal, a seal can be made with compressible gasket, a lip seal or an O ring. With metal to metal joints only an O ring is suitable. This is placed in a groove machined in either the end plate, the fermenter body or both. This seal ensures that a good liquid and or gas-tight joint is maintained in spite of glass or metal expanding or contracting at different rates with changes in temperature during sterilization cycle or an incubation cycle.

9. Temperature control
Provision of heat – fermenter in thermostatically controlled bath or by use of internal heating coils or by a silicone heating jacket through which water is circulated
Silicone jacket consists of silicone rubber mats wrapped around the vessel
Cooling surface/cooling water
Heat will be produced by microbial activity and mechanical agitation and if this heat is not adequate then heat needs to be added or removed.

10. Aeration and Agitation
Aeration – provide microorganisms in submerged culture with sufficient oxygen for metabolic requirements
Agitation – uniform suspension of microbial cells in homogeneous nutrient medium
Mechanical agitation is required in fungal and actinomycete fermentations

11. Structural components involved in aeration and agitation
Agitator (impeller)
Stirrer glands and bearings
Baffles
Aeration system (sparger)

12. Agitator (impeller)
Achieve mixing objectives – bulk fluid and gas-phase mixing, air dispersion, oxygen transfer, heat transfer, suspension of solid particles and maintaining uniform environment throughout vessel contents
Disc turbine could break up a fast air stream without itself becoming flooded in air bubbles

13. Baffles
Four baffles incorporated into agitated vessels of all sizes to prevent vortex and to improve aeration efficiency
Metal strips roughly one-tenth of vessel diameter and attached radially to the wall
Minimizes microbial growth on baffles and fermenter walls.

14. Aeration system (sparger)
Introduces air into liquid of fermenter
Three basic types – porous sparger
Orifice sparger – a perforated pipe
Nozzle sparger – an open or partially closed pipe
Combined sparger-agitator

15. Sterilization of the fermenter
Designed – for steam sterilization under pressure
Medium may be sterilized in vessel or separately and added aseptically
Steam should be introduced through all entry and exit points except the air outlet from which steam should be allowed to leave

16. Sterilization of air supply
Sterile air – large volumes in many aerobic fermentation processes
Heat (expensive) and filtration

17. Sterilization of exhaust gas from a fermenter
Sterilization of exhaust gas can be achieved by 0.2 μm filters on outlet pipe
Aerosol formation may occur in fermenter and moisture and solid matter may then plug filter
Filters – checked to ensure that no viable cells are escaping

18. Feed ports Addiiton of inoculum, nutrients and other supplements
Sampling ports to test
Additions of acid/alkali – silicone tubes pumped by peristaltic pumps after aseptic connection
In larger fermenter nutrient reservoirs and associated piping- integral parts – can be sterilized with vessel
Silicone tubes can be autoclaved separately.

19. Foam control Minimize foaming
Excessive foaming – danger that filters become wet resulting in contamination
Siphoning – loss of all or part of contents of fermenter

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against any beneficiary of programs financially assisted under Title I of the Workforce Investment Act of 1998 (WIA), on the basis of the beneficiary’s citizenship/status as a lawfully admitted immigrant authorized to work in the United States, or his or her participation in any WIA Title I-financially assisted program or activity.

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