OCR A Level Biology

Revision Notes

6.4.11 Batch & Continuous Fermentation

Batch & Continuous Fermentation

  • Microorganisms can be grown under controlled conditions in larger fermenters
  • The product of fermentation is either the microorganisms itself e.g. mycoprotein, or a product produced by the microorganism e.g. insulin
  • There are two main methods used to culture microorganisms by fermentation:
    • Batch fermentation
      • Microorganisms are grown in batches in the fermentation vessel
      • Once the culture cycle is complete, the product is removed, the fermenter is cleaned and a new batch of microorganisms is grown
      • This is known as a closed culture
    • Continuous fermentation
      • Microorganisms are continually grown and the products harvested
      • Nutrients are added and waste is removed throughout the culturing process

Maintaining optimum conditions in the fermenter

  • In order to maximise growth and productivity of the microorganisms, the fermenter must be carefully monitored and controlled to ensure conditions are optimum
  • The following factors are controlled:
    • pH – pH is monitored by probes and controlled to provide optimum pH for enzyme activity. This means rates of reaction are maximised and consequently so is growth and productivity of the microorganisms
    • Temperature – Optimum temperatures are maintained using a water jacket. This facilitates maximum enzyme activity and therefore maximum yield
    • Oxygen availability – Sterile air is pumped in to provide optimum oxygen to maximise respiration and therefore maximise yield
    • Nutrient supply – Nutrients are added and circulated, using paddles. to ensure microorganisms can access the nutrients required for maximum yield
    • Contamination – Contamination of the culture can lead to [popover id=1275705 label=”interspecific competition” for nutrients, oxygen and space, this will reduce product yield. Fermenters must be steam cleaned between cultures to prevent contamination
    • Waste removal – Waste products produced by the microorganisms can have a negative effect on the growth and productivity of the microorganisms. Waste products are constantly removed to prevent these toxic effects

Industrial fermenter, IGCSE & GCSE Biology revision notes

A fermenter is carefully monitored and controlled to ensure optimum conditions for growth of microorganisms. This will maximise yield of the required product

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