Using immobilised enzymes

Question 1

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

Answer 1

• less wasteful
  
  • whole microorganisms use up substrate gowing and reproduicng, producing biomass rather than product
• more efficient
  
  • work at high conc than possible when they are part of the whole microorganism
  • conditions ideal for product formation, may differ from those needed for organism growth
• specific
  
  • no unwanted enzymes, no unnecessary side reactions
• less donstream
  
  • pure product is produced by isolated enzymes
  • whole microorganisms give a variety of products in final broth

Question 2

Why are extracellular enzymes used over intracellular enzymes?

Answer 2

• generally easier and cheaper to use than intraceullar enzymes
• extracellular are secreted, making them easy to isolate and use
• each microorganism only produces a few extracellular enzymes, making it easier to identify and isolate the required enzymes, compared to intracellular
• extraceullular more robust, as conditions outside are less controlled than in the cyotplasm
  
  • deal with greater variations in temp and pH

Question 3

Why are intracellular enzymes still used?

Answer 3

• bigger range of intracellular enzymes
• provide the ideal enzymes for a process
• outweighs disadvantages

Question 4

How are enzymes immobilised?

Answer 4

• attached to an inert support system over which the susbtrate passes and is converted to product
• they can be recovered and used time after time

Question 5

What are the advantages of using immobilised enzymes?>

Answer 5

• reused
  
  • avoid expensive process of getting them
• easily separated from the reactiant and product of the reaction they are catalysing, less downstreaming
• more reliable
  
  • more control as the insoluble support provides a stable microenvironment for the enzymes
• greater temp tolerance
  
  • less easily denatured
  • work at larger range
• ease of manipulation
  
  • better altered to fit a particular process

Question 6

What are the disadvanatages of using immobilised enzymes?

Answer 6

• reduced efficiency
  
  • may reduce activity
• higher initial cost of materials
  
  • however do not need to be replaced
• higher initial cost of bioreaction=r
  
  • different system
• technical issues
  
  • more complex system, more things can go wrong

Question 7

What is surface immobilisation using adsorbtion? What are the adv and disadv?

Answer 7

• absorbition to inorganic carrier
• adv
  
  • simple and cheap to do
  • used with many differnt process
  • enzymes very accesible, activity virtually unchanged
• disadv
  
  • enzymes lost relatively easy

Question 8

What is surface immobilistation using covalent or ioninc bonding? What are the advantages and disadvantages?

Answer 8

• covalent or ionic bonding to inorganic carrier
• adv
  
  • cost varies
  • enzymes strongly bonded and unlikely to be lost
  • enzymes very accessible to substrate
  • pH and susbtrate conc often have little effect on enzyme activity
• disadv
  
  • cost varies
  • active site of the enzyme may be modified in process making it less effect

Question 9

What is entrapment in a matrix? What are the advantages and disadv?

Answer 9

• entrapped in a matrix / grid
• adv
  
  • widely applicable to different process
• disadv
  
  • expensive
  • difficult to entrap
  • diffusion of substrate to and product from the active site can be slow and hold up the reaction
  • effect of entrapment of activity depends on matrix, very variable

Question 10

What is encapsulation>

Answer 10

• entrapment in microcapsules or bejhind a semi-permeable membrane
• adv
  
  • relatively simple
  • small effect on enzyme activity
  • widely applicable
• disadv
  
  • relatively expensive
  • diffusion of the substrate to and product from the active site can be slow and hold up the reaction

Question 11

What is immobilised penicillin acylase used for?

Answer 11

• make semi-synthetic penicillins from naturally produced penicillinsw
• many bacteria produced resistance
• many are still vulnerable to semi-synthetic penicillin produced by penicillin acylase
  
  • very important in treating nfections