22.8 Using Immobilised Enzymes

Question 1

What are the advantages of using isolated enzymes (instead of whole organisms)?

Answer 1

• less wasteful
• more efficient
• more specific (no unwanted enzymes present so no wasteful side reactions take place)

Question 2

Isolated enzymes are extracellular, why are they easier and cheaper to use than intracellular enzymes?

Answer 2

• extracellular enzymes are secreted, making them easy to isolate and use
• each microorganism produces a few extracellular enzymes, making them easier to identify and isolate the required enzyme (in comparison each microorganism produced hundreds of intracellular enzymes which would need extracting from the cell)
• extracellular enzymes tend to be much more robust than intracellular enzymes (can cope with greater variation in temp and pH)

But intracellular enzymes are still sometimes used as theres a bigger range of them

Question 3

Examples of intracellular enzymes

Answer 3

Penicillin acylase

Question 4

Why are isolated enzymes immobilised?
What are immobilised enzymes?

Answer 4

Isolated enzymes used in industry can become mixed with the products of a reaction,
The products then need to be separated from this mixture, which can be complicated and costly
This is avoided in large scale production by using immobilised enzymes

Immobilised enzymes are enzymes that are attached to an insoluble material so they can’t become mixed with the products

Question 5

What are the three main ways enzymes are immobilised?

Answer 5

• encapsulated in jelly-like alginate beads, which act as a semi-permeable membrane
• trapped in a silica gel matrix
• covalent lay bonded to cellulose or collagen fibres

Question 6

How are immobilised enzymes used in industry?

Answer 6

The substrate solution for a reaction is run through a column of immobilised enzymes
The active sited of the enzymes are still available to catalyse the reaction but the solution flowing out of the column will only contain the desired product

Question 7

Advantages of using immobilised enzymes

Answer 7

• columns of immobilised enzymes can be washed and reused - this reduces costs because you dont have to keep buying new enzymes
• the product isnt mixed with the enzymes - no money or time spent on separating them out
• immobilised enzymes are more stable than free enzymes - theyre less likely to denature (tertiary structure is supported) in high temps or extremes of pH

Question 8

Disadvantages of immobilised enzymes

Answer 8

• extra equipment needed , which can be expensive
• immobilised enzymes are more expensive than free enzymes (so may not be economical for small scale production)
• the immobilisation of an enzyme can sometimes lead to a reduction in the enzyme activity because they can freely mix with their substrate

Question 9

Uses of immobilised enzymes

Answer 9

• conversion of lactose to glucose and galactose (for lactose free milk)
• production of semi-synthetic penicillins
• conversion of dextrins to glucose
• conversion of glucose to fructose (sweetener in food)