Describe how fermenters are used to produce penicillin from the fungus Penicillium on a large scale. Include in your answer the conditions that must be controlled inside the fermenter and explain why each condition is important.

Penicillium is inoculated into a liquid nutrient medium in a fermenter and the fungus grows, secreting penicillin into the broth. The penicillin is then isolated and purified from the broth.

The fermenter conditions that must be controlled are:
1. Temperature – kept at 25–30 °C. If the temperature is too high the fungus is killed or its metabolism is disrupted; if too low growth is inhibited.
2. pH – maintained at the optimum for Penicillium. A pH that is too acidic or too alkaline will damage the cells or stop growth.
3. Oxygen – supplied continuously. Penicillium requires oxygen for aerobic metabolism; insufficient oxygen limits growth and penicillin production.
4. Nutrients – the medium must contain the right carbon, nitrogen, vitamins and minerals. Lack of any essential nutrient stops growth or reduces yield.
5. Sterility – the fermenter must be free of other microorganisms. Contamination would compete for nutrients and reduce penicillin output.