4.1.8Use of Biological Resources
Industrial Fermenters — Edexcel International GCSE Science Double Award (Modular) - Biology Unit 2 Revision Notes & Topical Questions
5 min read 5 parts Lesson 9 of 15
Part 1 of 3What is a fermenter?
Purpose
- Purpose A fermenter is a large vessel in which bacteria or fungi are cultured in huge numbers.
- The microorganisms themselves, or the substances they make, are then collected.
Products
- Products Examples include the bacteria needed for yoghurt, mycoprotein, and antibiotics such as penicillin made by moulds.
- Genetically modified bacteria that make human proteins can also be grown in fermenters.
Main advantage
- Main advantage Conditions can be carefully controlled so that large quantities of exactly the right microorganism are produced.
Part 2 of 3Conditions controlled
Industrial fermenter
Aseptic precautions
- Aseptic precautions The vessel is cleaned with steam to kill other microorganisms,
- so only the desired species grows and the product is not contaminated.
Nutrients
- Nutrients A supply of sugar, mineral ions and other nutrients provides energy through respiration and materials for growth and reproduction.
Temperature
- Temperature Probes monitor it and a water jacket around the vessel warms or cools the contents to keep enzymes at their optimum.
pH
- pH A probe checks the pH and acid or alkali is added when needed, because enzymes work only in a narrow pH range.
Oxygen
- Oxygen Sterile air is bubbled in where aerobic respiration is needed.
Agitation
- Agitation Stirring paddles mix the contents so that microorganisms, nutrients, oxygen, heat and pH are even throughout.
Part 3 of 3Why optimum conditions matter
| If the condition is wrong | Effect on the culture |
|---|---|
| Temperature too high | Enzymes denature, so respiration and growth slow or stop |
| Temperature too low | Enzyme-controlled reactions are slow, so growth is slow |
| pH not at optimum | Enzymes work poorly or denature |
| Contaminating microorganisms present | They compete for nutrients and may spoil or contaminate the product |
| Not enough oxygen | Aerobic microorganisms cannot respire fully, so fewer are produced |
Key terms
| Term | Meaning |
|---|---|
| Fermenter | A vessel in which microorganisms are grown in controlled conditions on a large scale. |
| Aseptic | Free from unwanted microorganisms. |
| Water jacket | A layer of water around the vessel used to keep the temperature constant. |
| Agitation | Stirring that mixes the contents of the fermenter. |
| Mycoprotein | A protein-rich food made from a fungus grown in a fermenter. |
Avoid these mistakes
1
Saying that a fermenter is always anaerobic — many need oxygen supplied for aerobic respiration.
2
Stating that the temperature is controlled just by 'heating' — a water jacket removes excess heat too.
3
Forgetting to give a reasonalways link each control to enzymes, growth or contamination.
4
Confusing the sterilising step (before use, with steam) with pasteurising food.
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