22.8 Using Immobilised Enzymes Flashcards
What are the advantages of using isolated enzymes over whole microorganisms in biotechnological processes?
- ￬ WASTE
- substrate used up by microorganism for ￪ biomass, not making product
- ￪ EFFICIENCY
- Isolated enzymes can be kept in higher concentrations than within cell
- Can be kept at ideal conditions for product formation (which may be unsuitable for microorganism)
- ￪ SPECIFICITY
- No unwanted enzymes present
- ∴ no wasteful side reactions
- No unwanted enzymes present
- ￬ DOWNSTREAM PROCESSING
- immobilised enzymes produce pure product
- does not require separation of product from contaminants/enzymes afterwards
- immobilised enzymes produce pure product
Why may extracellular enzymes be isolated instead of intracellular enzymes?
- EASIER TO ISOLATE
- extracellular enzymes secreted outside cell
- EASIER TO IDENTIFY
- each organism produces few types of extracellular enzymes but many types of intracellular enzyme
- MORE ROBUST
- conditions outside cell are less controlled
- extracellular enzymes are better adapted to changes in temperature + pH
- conditions outside cell are less controlled
Why may intracellular enzymes be isolated instead of extracellular enzymes?
greater variety of intracellular enzymes than extracellular
∴ there may not be a suitable extracellular enzyme to choose from
What are the advantages of immobilising enzymes?
- Can be reused
- Greater temperature tolerance
- Altered easier than free enzymes
- More reliable (due to higher degree of control over stable microenvironment)
What are the disadvantages of immobilising enzymes?
- May reduce enzyme activity
- More expensive
- Higher initial bioreactor costs (requires a different system from traditional fermenters)
- More technical issues (reactors for immobilised enzymes are more complex than simple fermenters)
What are the disadvantages of immobilising enzymes?
- May reduce enzyme activity
- More expensive
- Higher initial bioreactor costs (requires a different system from traditional fermenters)
- More technical issues (reactors for immobilised enzymes are more complex than simple fermenters)
What are the different methods of immobilising enzymes?
- SURFACE IMMOBILISATION
- Adsorption to inorganic carrier
- Covalent/ionic bonding to inorganic carrier
- ENTRAPMENT
- In matrix
- Encapsulation
What are the advantages & disadvantages of isolating enzymes which are adsorbed to inorganic carriers?
- ADVANTAGES
- Simple & cheap
- Enzymes are accessible
- Enzyme activity is unaffected
- DISADVANTAGES
- Enzymes can detach supporting material easily
What are the advantages & disadvantages of immobilising enzymes using covalent/ionic bonding to inorganic carriers?
- ADVANTAGES
- Enzymes strongly bound, ∴ do not easily detach from carrier
- pH & substrate concentration have little effect on enzyme activity
- DISADVANTAGES
- Additional bonding may change shape of active site
What are the advantages & disadvantages of immobilising enzymes by entrapment in a matrix?
- ADVANTAGES
- Widely applicable to different processes
- DISADVANTAGES
- Difficult to entrap
- Entrapment may affect enzyme activity
What are the advantages & disadvantages of immobilising enzymes by encapsulation?
- ADVANTAGES
- Simple
- Little effect on enzyme activity
- DISADVANTAGES
- diffusion of reactant/product to/from active site slows reaction
When immobilising isolated enzymes to a carrier, what properties should the carrier have?
- INSOLUBLE
- CHEMICALLY INACTIVE
When immobilising isolated enzymes by encapsulation, what property should the membrane have?
SEMI-PERMEABLE
to allow diffusion of products/reactants in & out of the active site
Immobilised enzymes
Which enzyme converts glucose ⟶ fructose?
glucose isomerase
Immobilised enzymes
Which enzyme converts lactose ⟶ glucose + galactose?
lactase
