Describe how a fermenter is used to produce penicillin from Penicillium, and explain why the conditions inside the fermenter must be carefully controlled.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Penicillium is inoculated into a liquid nutrient medium and grown in a fermenter.
The fungus secretes penicillin into the medium; the antibiotic is then isolated, extracted and purified from the broth.
The temperature inside the fermenter is kept at 25–30 °C so the organism is not killed and grows at its maximum rate.
The pH is maintained at the optimum value; this prevents the microorganism from being killed or its growth inhibited and also excludes or kills unwanted microorganisms that could contaminate the culture.
The fungus secretes penicillin into the medium; the antibiotic is then isolated, extracted and purified from the broth.
The temperature inside the fermenter is kept at 25–30 °C so the organism is not killed and grows at its maximum rate.
The pH is maintained at the optimum value; this prevents the microorganism from being killed or its growth inhibited and also excludes or kills unwanted microorganisms that could contaminate the culture.
Examiner tips
- Use the words ‘inoculated’, ‘grown’, ‘secretes’, ‘isolated’, ‘purified’ to show the process. Show the temperature range 25–30 °C and explain it keeps the fungus alive and maximises growth. Mention pH control to prevent inhibition and contamination.
Common mistakes
- Writing the temperature as a single value instead of a range. Forgetting to state that penicillin is secreted into the medium. Not linking pH control to both inhibition of the main culture and exclusion of contaminants.
Mark scheme (4 marks)
- Penicillium is cultured / grown in a liquid nutrient medium inside the fermenter
- Penicillin is secreted by Penicillium and is then isolated / extracted and purified
- Temperature must be maintained at the optimum (25–30 °C) so that the microorganism is not killed / grows at the maximum rate
- pH must be controlled at the optimum so the microorganism is not killed / to prevent growth being inhibited; OR undesired microorganisms must be excluded / killed to prevent contamination and competition
Key terms in this question
fermenter · Penicillium · penicillin
Related
- All Cambridge International IGCSE Biology (0610) revision notes →
- How to answer a "Describe and Explain" question →
- Decode the mark scheme abbreviations →
More Biotechnology questions
- Describe how pectinase is used in the production of fruit juice, and explain why…
- Explain why biological washing powders are able to remove food stains from cloth…
- Describe how lactase is used to produce lactose-free milk, and explain why this …
- Describe how yeast is used in bread-making and explain how the process causes do…