IGCSE Biology / Using microorganisms
Growing microorganisms at scale revision notes
Edexcel International GCSE Biology (4BI1), chapter 21: Using microorganisms, specification point 5.8. Free lesson.
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Industrial fermenters provide controlled conditions for microorganisms to grow and make useful products. Each part of the vessel helps prevent a factor from limiting growth or contaminating the product.
How an industrial fermenter is built
A fermenter is a large vessel with equipment to control conditions throughout the tank. Each part has a purpose, so a good label includes what the part does. The stainless steel vessel is easy to sterilise and does not react with its contents. The stirrer keeps microorganisms suspended in the liquid and spreads heat evenly. The air inlet supplies oxygen for aerobic respiration and helps mix the contents. The water jacket surrounds the vessel and removes heat released during fermentation. Temperature and pH probes monitor conditions continuously, so they can be corrected.…
Why conditions are controlled
Microorganisms grow best when conditions suit their enzymes. If a condition moves away from its optimum, growth may slow or stop, so explain what would go wrong without each control. Temperature: it is kept near the enzyme optimum. Too low slows growth; too high denatures enzymes, changing their shape so they no longer work properly. pH: it is kept near the optimum for the enzymes. Fermentation often produces acid, so pH needs continuous correction. Oxygen: the air inlet supplies oxygen for aerobic respiration, which releases far more energy per glucose than anaerobic respiration.…
Products made in fermenters
Fermenters can grow different microorganisms to make useful products. After production, each product is separated from the mixture, purified and packaged. Penicillin is made by growing the fungus *Penicillium*. It is produced when nutrients run low, so the process is run in batches. Mycoprotein is a protein food made by growing the fungus *Fusarium* on glucose syrup. Oxygen and ammonia are supplied. Insulin is made using genetically modified bacteria.
Batch and continuous production
The production method depends on when the product is made and how nutrients are supplied. Penicillin is made in batches because the fungus produces it when nutrients run low. Mycoprotein is made continuously, with nutrients fed in and product drawn off.