Temperature, type and time of nutrient added, oxygen concentration and pH.
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Why does temperature need to be controlled?
Too hot and enzymes will denature. Too cold and growth will be slowed.
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How does type and time of addition affect growth of microorganisms
Growth requires a supply of nutrients. Timing can be manipulated depending on whether the process is designed to produce a primary or secondary metabolite.
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Why must oxygen concentration be controlled
Done under aerobic conditions so oxygen needed. Lack of oxygen leads to unwanted products of anaerobic respiration and reduction in growth rate.
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Why must pH be controlled?
Changes in pH in the fermentation tank can reduce the activity of enzymes and so reduce growth rates.
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What is the role of the pressure vent?
Prevents any gas build-up.
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What is the role of an air inlet
Sterile air provides oxygen in aerobic fermenters.
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What does the water jacket inlet allow?
Allows circulation of water around the fermenter to regulate temperature.
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What is the role of the outlet tap?
For draining fermenter
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Why is a motor used?
Rotates the blades to mix the culture evenly.
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What is the inlet for?
For the addition of nutrients
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What are the electronic probes for?
For measuring oxygen, pH and temperature levels.
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Describe what air outlets are used for
Air bubbles out from outlets, mixing with culture.
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What are all inlets and outlets fitted with?
Fitted with filters to prevent contamination.
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Describe a batch culture
The microorganism starter population is mixed with a specific quantity of nutrient solution then allowed to grow for a fixed period with no further nutrient added.
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What happens at the end of the period?
At the end, the products are removed and the fermentation tank is emptied. Penicillin in produced through batch culture.
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Describe a continuous culture
Nutrients are added to the fermentation tank and products removed from the fermentation tank at regular intervals. E.g. insulin/genetically modified bacteria.
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What is any unwanted microorganism called?
A contaminant.
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What do unwanted microorganisms do?
Compete for nutrients and space. Reduce yield of useful products and cause spoilage by producing toxic chemicals. Destroy culture and products.
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What does the term aseptic technique refer to?
Measures taken to ensure asepsis (contamination of the culture) does not occur at any point.
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Describe the advantages of batch culture
Easy to set up and maintain. Only one batch is lost if contamination occurs. Useful for secondary metabolites.
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What are the disadvantages of batch culture?
Less efficient as fermenter is not in operation at all times, growth rate is slower.
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What are the advantages of continuous culture?
Growth rate is higher as nutrients are continuously added, more efficient as continuous, useful for primary metabolites.
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What are the disadvantages of continuous culture?
Set up is more difficult, if contamination occurs, huge volumes are lost.
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Describe the aseptic techniques at starter culture level
Sterilised before and after using a flame glowing/UV light. Work carried out in a fume cupboard and cultures kept closed where possible.
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What are the aseptic techniques used at large-scale culture level?
Washing, disinfecting and steam-cleaning when not in use. Surfaces made of polished stainless steel and all nutrient media fermenter sterilised. Fine filters on inlet and outlet.
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Other cards in this set
Card 2
Front
Why does temperature need to be controlled?
Back
Too hot and enzymes will denature. Too cold and growth will be slowed.
Card 3
Front
How does type and time of addition affect growth of microorganisms
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