Industrial Microbiology INDM 4005 Lecture 6 17/02/04. Questions for today:. 1. What is a fermentation system? 2. What is the most widely used fermenter? 3. What are the other types of fermenter? 4. How do you control a fermentation system? 5. Why is mass transfer important?.
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Types of Process
Stirred Tank Reactor
The basic function of a fermenter is to provide a suitable environment in which an organism can efficiently produce a target product that may be
- cell biomass,
- a metabolite,
- or bioconversion product.
What it should be capable of;
- non-stirred, non-aerated
- non-stirred, aerated
- stirred, aerated
(Beer and wine)
(Biomass, eg Pruteen)
- temperature, concentration, pressure, specific heat
- mass, volume, entropy and energy
(i). Nature of microbial (or mammalian, plant tissue) cell;
(a) Hydrodynamic characteristics
(b) Mass and Heat Transfer
(d) Genotype and Phenotype
(ii). Environmental Control and Monitoring of the process;
(a) pH, temperature, dissolved oxygen etc.
(b) Asepsis and avoidance of contamination
(iii). Process factors;
(a) Effect on other unit operations
(c) Potential for scale-up
Stirred Tank Reactor
The function of the agitation system is to
Agitator design and operation
Radial flow impellers - Rushton turbine
The most commonly used agitator in microbial fermentations
Like all radial flow impellers, the Rushton turbine is designed to provide the high shear conditions required for breaking bubbles and thus increasing the oxygen transfer rate.
Oxygen Mass Transfer Steps
1. Bioreactor size - to provide required production capacity
2. Mass transfer - to provide nutrients to cells, well dispersed, adequate oxygen etc
3. Control systems
(a) temperature, pH, etc.
(b) sterilisation/ aseptic operation
(c) representative sampling
(d) heat transfer - example sterilisation of media
4. Requirement for asepsis / containment