6.4.9(immobilised enzymes)

State the use of downstream processing

• when mobile enzymes need to be separated from the products which can be complicated and costly

What is the equation of calculating the number of bacteria in 1cm3 of solution after using serial diltution

• Number of bacteria = number of colonies/(serial dilution factor*volume of solution used)

Give 3 benefits of using immobilised enzymes

• They can be reused

• No downstream processing costs - product enzyme is free

• Immobilised enzymes are more stable than free enzymes - more tolerant to pH and temperature changes

Give 3 disadvantages of immobilised enzymes

• Extra equipment is needed - can be expensive

• Immobilised enzymes are more expensive to buy than free enzymes - not economical in small-scale

• Immobilisation techniques can reduce enzyme activity as they are not free to mix with substrate

Name the 3 methods of immobilising enzymes

• Adsorption

• Cross-linking

• Entrapment or encapsulation

Describe how adsorption can be used to immobilise enzyme and give 3 examples of support materials

• Ionic bonds bind enzymes to support material with active site exposed and accessible to the substrate

• eg:

  • Clay

  • Glass beads

  • Resins

Give 2 disadvantages of using adsorption to immobilise enzymes

• Active site may be slightly distorted, reducing activity

• Risk that enzymes could detach and contaminate product

Describe how Cross-linking can be used to immobilise enzyme and give 3 examples of support surfaces

• Enzymes attached by covalent bonds to a supporting surface

• eg:

  • Clay

  • Cellulose

  • Collagen fibres

Give 2 disadvantages of using Cross linking to immobilise enzymes

• Active sit may be distorted, reducing activity

• Expensive process

Describe how entrapment can be used to immobilise enzymes and give 3 materials which can be used for entrapment

• Enzyme molecules are trapped in a matrix

• substrates can diffuse into matrix and form a product then diffuse out

• Eg:

  • Calcium alginate

  • Beads

  • Silica gel matrix

State a disadvantage of using entrapment to immobilise enzymes-

• Only suitable for small substrates and products, as they have to enter and leave the entrapment matrix

Describe the process of making lactose free milk

• Alginate beads containing immobilised lactase can be tightly packed into a column

• The liquid substrate can be trickled over the beads

• The lactase breaks down the lactose in the milk and the product then trickles out the bottom of the column

• The product is then collected and purified

Name 6 enzymes which are immobilised to be used in industry

• Glucose isomerase

• Lactase

• Glyco amylase

• Aminoacyclase

• Penicillin acylase

• Nitrilase

Describe the use of Glucose isomerase in industry

• converts glucose to fructose which is used to sweeten drinks

Describe the use of Lactase in industry

• Converts lactose to sweeter sugars - glucose and galactose.

• Used to make lactose free milk and condensed milk

Describe the use of Glucoamylase in industry

• Converts dextrins to glucose and glucose syrup which are used in food industry to sweeten and thicken foods

Describe the use of Aminoacyclase in industry

• Separates a L and D amino acids from a mixture.

• Only L form can be used by the body and used in production of dietary supplements

Describe the use of Penicillin acylase in industry

• Changes the structure of penicillin to make semi-synthetic penicillin that will fight a wider range of bacteria

Describe the use of Nitrilase in industry

• Converts acrylonitrile to acrylamide which is used to make plastics

• Used in the production of the polymer which makes nappies absorbent