Enzyme Activity: Immobilised v Free (CIE AS Biology)

• Enzymes can be added to solutions and are thereby considered ‘free’ or they can be immobilised
  • Investigations with free enzymes are carried out with an enzyme added to a solution
  • Depending on the needs of an investigation, substrate can be added directly to the solution or the enzyme solution can be added in a more controlled way to a substrate
• Immobilised enzymes are enzymes that have been bound to an inert, stationary and insoluble material such as alginate
• The substrate is then passed over the immobilised enzyme and the product is collected
• Advantages to this method:
  • There is no enzyme in the product (the product is uncontaminated) and therefore there is no need to further process or filter the end product
  • The immobilised enzyme can be reused multiple times which is both efficient and cost-effective (enzymes are expensive)
  • Immobilised enzymes have a greater tolerance of temperature and pH changes (immobilisation often makes enzymes more stable)
• A practical application of immobilised enzymes used in the food industry is in the production of lactose-free milk:
  • Milk is a valuable source of nutrients containing protein, fat and the carbohydrate lactose
  • Lactose is a disaccharide that is broken down into glucose and galactose
  • 5-10% of the UK population are lactose intolerant

Immobilised Enzymes Diagram

Using immobilised enzyme to modify milk

• Using the enzyme lactase, as shown above, is an efficient way to remove lactose from milk and to provide lactose intolerant individuals with a way of consuming milk without suffering intolerance symptoms:
  • The enzyme lactase can be immobilised using alginate beads
  • Milk is run through the column of lactase-containing beads
  • The lactase hydrolyses the lactose in the milk to glucose and galactose
  • This ensures the milk is lactose-free
  • It can also then be used to make other lactose-free dairy products

Breakdown of Lactose Diagram

Lactose is a disaccharide that is broken down by lactase into the monosaccharides glucose and galactose