6.4.9: Immobilized enzymes

Question 1

What are the advantages of immobilising enzymes?

Answer 1

• Held in place, not able to diffuse through the solution.
• Can be reused.
• Extraction costs are lower.
• The continuous process made easier, no cells requiring nutrients and releasing waste products.
• Immobilising matrix protects against extreme conditions.

Question 2

What are the disadvantages of immobilising enzymes?

Answer 2

• Setting up immobilised enzyme process is more expensive.

- Immobilised enzymes are less active than free enzymes (the process is slower).

Question 3

Describe adsorption.

Answer 3

Enzyme molecule bound to supporting surface by ionic links and hydrophobic interactions.

Question 4

What are the disadvantages to adsorption?

Answer 4

• Active site may be distorted by additional interactions

- Bond forces not always strong, enzymes may detach and leak into the reaction mixture.

Question 5

Describe covalent bonding.

Answer 5

Enzyme molecule bound to supporting surface by strong covalent bonds.

Question 6

What are the disadvantages to covalent bonding?

Answer 6

• Production of covalent bonding can be expensive.

- Active site could be distorted.

Question 7

Describe entrapment

Answer 7

• Immobilised enzymes held in a network of cellulose fibres.
• Substrate and product molecules can pass through cellulose fibres.

Question 8

What are the advantages of entrapment?

Answer 8

-Enzyme active site not affected so the enzymes remain fully active.

Question 9

What are the disadvantages of entrapment?

Answer 9

-Only suitable for processes where substrate and product molecules are relatively small so that they can diffuse in and out of the entrapment matrix.

Question 10

Describe membrane separation.

Answer 10

Enzyme molecules separated from reaction mixture by partially permeable membrane.

Question 11

What are the disadvantages of membrane separation?

Answer 11

• substrates and products must be small enough to pass through the partially permeable membrane.
• This limits access to enzymes and may limit the rate of reaction.

Question 12

What is glucose isomerase used to do?

Answer 12

glucose→fructose

• Make HFCS
• sweeter than sucrose
• Diet foods and diabetic foods.

Question 13

What is the use of aminoacylase?

Answer 13

• A hydrolase
• Removes nitrogen from L-acyl-amino acids
• Produces L-amino acids used in pharmaceutical compounds.

Question 14

What is the use of glucoamylase?

Answer 14

Dextrins(polymer of glucose)→glucose

Used to digest sources of starch. (fermentation of corn and cassava)

Question 15

What is the use of Nitrile hydrase?

Answer 15

Nitriles→amides
e.g. Acrylonitrile→Acrylamide→polyacrylamide
Use:
-Treatment of water
-Sticks pollutants together
-pollutants precipitated out