immobilised enzymes

Question 1

what are immobilised enzymes

Answer 1

enzymes that are held in place (taken out of suspension) and not free to mix with the substrate

Question 2

what are the advantages of using enzymes that have been immobilised

Answer 2

-no mixing with product, lower extraction costs
-easy reuse
-continuous process is easier to set up = no cells needing nutrients, reproducing or releasing waste
-enzymes are surrounded by immobilising matric, making them more stable and protects them, higher temps and wider pH range can be used without denaturing

Question 3

what are the four methods of enzyme immobilisation

Answer 3

1. adsorption
   2.binding
2. entrapment
   4.encapsulation

Question 4

explain adsorption and any problems with the method

Answer 4

-enzymes are adsorbed (attached onto) the surface of an insoluble/ inert support material e.g clay, porous carbon, glass beads and resin

-active site may be slightly distorted by the process, bonding forces are weak so some enzyme may detach and leak into the reaction mixture

Question 5

explain binding and possible problems with it

Answer 5

-enzymes bound to insoluble/ inert support materials like cellulose or collagen fibres by covalent or ionic bonds

-more expensive, could distort active site but are less likely to detach

Question 6

explain entrapment and possible problem

Answer 6

enzyme trapped in a matrix e.g. silica gel or a microcapsule
-substrate molecule must be able to diffuse into the entrapment matrix and products diffuse out (only works on relatively small molecules)

Question 7

explain encapsulation and possible problems

Answer 7

-enzymes may be contained in a partially permeable membrane e.g semi permeable alginate beads
-substrate and product must be small enough to diffuse through the membrane- might limit rate of reaction

Question 8

what are examples pf immobilised enzymes in biotechnology

Answer 8

-glucose isomerase to convert glucose to fructose
-glucoamylase to convert dextrins to glucose
-lactase for hydrolysis of lactose to glucose and galactose
-penicillin acylase for formation of semisynthetic penicillin which some penicillin resistant organisms are not resistant
-aminoacylase for production of pure samples of L-amino acids