Using immobilised enzymes

What are isolated enzymes and why are they used?

Extracted enzymes from organisms, they are a lot more efficient than using a whole microorganism

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What are some of the advantages of using isolated enzymes over whole microorganisms?

Less wasteful (whole MO's use substrate for growing as well), more efficient (can work at much higher concentrations than in MO's), More specific, Less downstream processing (pure product formed), conditions can be made specific to enzyme and not MO

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Why do scientists tend to use extracellular enzymes over intracellular enzymes?

Extracellular are secreted so easier to isolate, relatively few extracellular so easier to identify, they are more robust as they can work in outside conditions meaning they can cope with wider variations of temperature and pH

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When might intracellular enzymes be used?

There are a bigger range of intracellular enzymes so when there is an enzyme that may do a better job as it is more specific it is used, if the effectiveness outweighs the cost of extraction etc it is used

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What are immobilised enzymes?

Enzymes which are attached onto an inert support system over which the substrate can pass and be converted to product

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Why do we use immobilised enzymes?

The enzymes can be recovered from the reaction mixture unlike the free enzymes, making it more economical

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Advantages of using immobilised enzymes

Cheaper (can be reused, easily separated so less downstream processing), more reliable (high degree of control over process), greater temperature tolerance (bioreactor less expensive to run)

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Disadvantages of using immobilised enzymes

Reduced efficiency (can reduce its activity rate), Higher initial cost (immobilised enzymes are expensive, different type of bioreactor needed which is more expensive) More technical issues (more complicated bioreactor so more things can go wrong)

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How can enzymes be immobilised?

Surface immobilisation- by adsorption or covalent or ionic bonds, entrapment- by matrix or in a microcapsule/ semi-permeable membrane capsule

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Adsorption to inorganic carriers (e.g. cellulose, silica)

Adv- cheap and simple, used in many different processes, enzymes accessible to substrate, Dis- enzymes can be easily lost

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Covalent and ionic bonding to inorganic carriers (e.g. C- carriers with carboxyl, hydroxyl amino groups, I- polysaccharides, synthetic polymers)

Adv- strongly bonded, very accessible to substrate, Dis- Active site may be modified in process making it less effective

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Entrapment by matrix (e.g. gelatin, activated carbon)

Adv- Widely acceptable to different processes, Dis- expensive, difficult to entrap, diffusion of substrate to and product from enzyme slow so reaction can be held up, entrapment can affect enzyme activity

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Entrapment by membrane (e.g. polymer based semi-permeable membranes)

Adv- Simple to do, small effect on enzyme activity, widely acceptable to different processes, Dis- Expensive, diffusion can be slow and hold up reaction process

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Immobilised Lactase

Used to remove lactose from milk to glucose and galactose, people can be lactose intolerant

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Immobilised glucoamylase

Used to complete the breakdown of starch into glucose syrup, after amylase has broken down starch into dextrins (short chain polymers), the immobilised glucoamylase enzymes breaks down the dextrins to glucose

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Immobilised aminoacylase

Produces pure samples of L-amino acids used in the production of pharmaceuticals

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Using immobilised enzymes

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