- Modern biotechnology often involves big steel vessels, called fermenters, in which microorganisms are grown. Inside these fermenters, the microorganisms are provided with exactly the right conditions to encourage them to grown and produce the substances we desire.
- For example, the fungus Pencillium is used to produce the antibiotic penicillin.
- Before the microorganism is put into the fermenter, it is essential to kill all other microorganisms already in there as they might grow instead (sterilisation).
- Not doing this would cause a problem as these unwanted microorganisms will use up the nutrients given into the fermenter and not allow the desired microorganism to grow to the largest yield.
- The fermenter is sterilised using high-pressure steam. Everything that is added to the fermenter is first sterilised before entering to prevent microorganisms getting into the culture (contamination).
- These are called aseptic precautions.
- Optimal conditions for the microorganism are supplied, so that it produces as much product as possible in the shortest time. These conditions include:
- NUTRIENTS: sources of carbohydrates (energy) and nitrogen (nitrates, to make proteins) are added such as sugar and ammonium ions. This is added to the food culture medium.
- AN OPTIMUM TEMPERATURE: this is so the enzymes in the microorganism can work at a fast rate but don’t get denatured. As the microorganisms produce heat by respiration, the fermenters must be cooled using a water jacket.
- OPTIMUM PH: the enzymes work best at this pH.
- OXYGEN: this is provided by bubbling sterile air into the fermenter, so the microorganism can respire aerobically.
- AGITATION: produced by a stirrer, to mix the oxygen and nutrients into all of the liquid.
Factors affecting growth in yeast
- Yeasts are widely used in biotechnology for making bread and alcoholic drinks such as beer and wine. Yeast can also be grown on an industrial scale in fermenters to produce enzymes and medicines such as penicillin.
- The pH of the culture is one of the factors controlled in the fermenter to create optimum conditions. If the pH is too acidic or too alkaline, the yeast enzymes do not function properly.
- As a result, the yeast does not respire and grow and it may die.