Immobilised enzymes are widely used in industry

• Just before 1900, it was discovered that enzymes could be used to catalyse production of alcohol in the absence of yeast cell
• Since then, hundreds of enzymes have been developed outside of living cells for?commercial purposes
• Uses of enzymes in industrial processes can be?expensive,?so we need ways to?reuse?them in order to be cost-effective
• An?immobilised enzyme?is an enzyme that is attached to an?insoluble material?to prevent mixing with the product and through this method, the enzyme can be?reused?in subsequent reactions
• Immobilised enzymes are used in the following commercial processes
  • Agriculture
  • Biosensors (diagnosis, analysis eg. for impurities)
  • Manufacturing processes
  • Energy generation
  • Environmental management
  • Food/drinks industry
  • Medicines
• Methods by which enzymes can be immobilised include:
  • Attachment to an?inert substance?eg. glass
  • Entrapment within a?matrix?e.g. alginate gel
  • Entrapment within a?partially permeable membrane

Different ways in which enzymes can be immobilised

• The mechanism of immobilised enzyme use works as follows:
  • The immobilised enzymes are contained within a?column
  • The substrate is?filtered through?this column in?solution
  • As the substrate runs through the column,?enzyme-substrate complexes?are formed and products are produced
  • These products then?flow out?of the column,?leaving the enzymes behind?to catalyse the reaction again

The immobilised enzymes are contained within a column

Advantages of immobilised enzymes

• 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?(many enzymes are?expensive)
  • Reusing the enzyme also?avoids the need to separate?the enzyme from the product in downstream processing
• Immobilised enzymes have a?greater tolerance of temperature and pH changes?(immobilisation often makes enzymes more?stable)
• Substrates can be exposed to?higher enzyme concentrations?than when using enzymes in solution, increasing the rate of throughput
• Conditions can be?controlled carefully, allowing immobilised enzymes to function?close to their optimum conditions?and be?more stable

Disadvantages of immobilised enzymes

• Specialist?expensive equipment?is required
• Immobilised enzymes are?more costly to buy, so are unlikely to be financially worthwhile for?smaller industries
• The?rate of reaction is sometimes lower?when using immobilised enzymes as the enzymes cannot mix freely with the substrate

Examples of immobilised enzymes in industry

A closer look at lactose-free milk production

• • Milk?is a valuable source of nutrients containing protein, fat and the carbohydrate?lactose
  • 5-10% of the UK population are?lactose intolerant
    • They can't digest lactose and?suffer?from bloating, digestive problems, discomfort and pain
  • Lactose is a?disaccharide?that is hydrolysed into?glucose?and?galactose
  • The yeast?Kluyveromyces lactis?grows naturally in milk and can be cultured as a source of the enzyme?lactase
  • Glucose and galactose are?sweeter than lactose, so less sugar needs to be added to foods with modified lactose?to achieve the same sweetness
  • Ice cream?and?yoghurt?production also benefit from having more glucose and galactose than lactose in the milk they are made from

Using the immobilised enzyme lactase to modify milk