A fermenter (bioreactor) is a large vessel in which microorganisms are grown under controlled conditions, so that growth and product yield are as high as possible.
• Temperature: enzymes work best at an optimum. Too cold slows growth; too hot denatures enzymes. Respiring microorganisms release heat, so a water jacket with cold water circulating removes excess heat. A temperature probe monitors it.
• pH: enzymes have an optimum pH, and waste products (such as CO2 or acids) change the pH. A pH probe monitors it, and acid or alkali (or a buffer) is added to correct it.
• Oxygen: most industrial microorganisms respire aerobically. Sterile air is bubbled in through an air inlet (sparger). Too little oxygen reduces growth and may cause unwanted anaerobic products.
• Mixing: motor-driven paddles (impellers) stir the culture, so nutrients, oxygen and heat are spread evenly and cells stay in suspension.
• Nutrients: sterile nutrient medium is supplied through an inlet (at the start in batch culture, continuously in continuous culture).
• Sterility: the vessel is steam-sterilised before use, and all inputs (air, nutrients) are sterile, to prevent contamination by other microorganisms that would compete, reduce yield or spoil the product.A product outlet allows the culture to be removed, and the product is then separated and purified (downstream processing).
• Temperature: enzymes work best at an optimum. Too cold slows growth; too hot denatures enzymes. Respiring microorganisms release heat, so a water jacket with cold water circulating removes excess heat. A temperature probe monitors it.
• pH: enzymes have an optimum pH, and waste products (such as CO2 or acids) change the pH. A pH probe monitors it, and acid or alkali (or a buffer) is added to correct it.
• Oxygen: most industrial microorganisms respire aerobically. Sterile air is bubbled in through an air inlet (sparger). Too little oxygen reduces growth and may cause unwanted anaerobic products.
• Mixing: motor-driven paddles (impellers) stir the culture, so nutrients, oxygen and heat are spread evenly and cells stay in suspension.
• Nutrients: sterile nutrient medium is supplied through an inlet (at the start in batch culture, continuously in continuous culture).
• Sterility: the vessel is steam-sterilised before use, and all inputs (air, nutrients) are sterile, to prevent contamination by other microorganisms that would compete, reduce yield or spoil the product.A product outlet allows the culture to be removed, and the product is then separated and purified (downstream processing).