Fermentation

• ❑ Conversion of sugar into ethanol and CO2
• ❑ Some fermentations are aerobic, some are anaerobic
• Laboratory fermentations:

  ❑ Growing bacteria or yeast

  ✓ Aerobic/anaerobic

  ❑ Tubes, flasks, fermenters

  ❑ Volumes 1 ml up to 20 litres

  ❑ Various applications

  ✓ Alcohol production ✓ Plasmid purification ✓ Protein purification
• Beer:

  ❑ Saccharomyces cerevisiae

  ❑ Improve drinking water safety

  • Reduction in pH >4.5

  • Reduction in nutrients

  • Increase in alcohol

  • Addition of hops
• Cheese production:

  ❑ Lactic fermentation of milk

  • Lactobacillus lactis

  • Streptococcus thermophilus

  • Rennet
• Cheese production:

  ❑ Additional ripening

  • Swiss cheese

  • Propionibacterium shermanii

  ❑ Roquefort • Penicillium roquefortii

  ❑ Camembert

  • Penicillium camemberti
• Lactic fermentation of milk


  The process of adding bacteria to milk to convert lactose into lactic acid, thickening the milk and giving it a tangy flavor.
• Lactobacillus lactis


  A type of bacteria used in lactic fermentation that produces lactic acid slowly, resulting in a milder flavor.
• Streptococcus thermophilus


  A type of bacteria used in lactic fermentation that produces lactic acid quickly, resulting in a stronger flavor.
• Rennet


  An enzyme added to milk after lactic fermentation that causes the milk to coagulate, or form curds, which are then used to make cheese.