immobilised enzymes

• • enzymes produced by microbes have an importance in industry, medicine and food technology
  • enzymes are not used up in the reaction and remain in the suspension
  • the product must be isolated from the enzyme before use
  • extraction costs are reduced
  • enzymes are reused
  • can be made into a continuous process with less waste
• methods for immobilising enzymes

  • entrapment
  • adsorption
  • covalent bonding
  • membrane separation
• entrapment

  • enzymes trapped in gel bead
  • reaction rates may be reduced as substrate must penetrate trapping medium (active site less easily available)
  • the product molecules must diffuse out of the gel bead matrix
  • only suitable for small substrate and product molecules that diffuse easily
• adsorption

  • enzymes bind to immobilising support (glass beads) by hydrophobic interactions and ionic links.
  • leakage can occur as bonds are not strong and they can become detached.
  • high reaction rates as active sites remain unchanged and exposed for accessibility to the substrate
• covalent bonding

  • enzymes are bonded to surfaces using a cross linking agent such as gluteraldehyde to link enzyme to insoluble clay.
  • binding strong (little leakage - detachment) but some covalent bonding can distort the shape of the active site
• membrane separation

  • enzymes are separated by partially permeable membrane. the substrate and product molecules must be small enough to move across membrane to access the active site