The advantages of immobilisation are
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prevention of losses due to flushing away of enzyme
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a more stable enzyme
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the possibility to produce an enzymes with altered properties
immobilised enzymes and cells, enzyme reactors, biosensors, use of enzymes and enzyme inhibitors for commercial and medical purposes, secondary plant metabolism.
Immobilisation can greatly effect the stability of an enzyme. If the immobilisation process introduces any strain into the enzyme, this is likely to encourage the inactivation of the enzymes under denaturing conditions (e.g. higher temperatures or extremes of pH). However where there is an unstrained multipoint binding between the enzyme and the support, substantial stabilisation may occur (). This is primarily due to the physical prevention of the large conformational changes within the protein structure which generally precede its inactivation. Many successful covalent immobilisation processes involve an initial freely-reversible stage, where the covalent links are allowed to form, break and re-form until an unstrained covalently-linked structure is created, in order to stabilise the resultant immobilised enzyme. Additional stabilisation is derived by preventing the enzyme molecules from interacting with each other, and the protection that immobilisation affords towards proteolytic and microbiological attack. This latter effect is due to a combination of diffusional difficulties and the camouflage to enzymic attack produced by the structural alterations. In order to achieve maximum stabilisation of the enzymes, the surfaces of the enzyme and support should be complementary with the formation of many unstrained covalent or non-covalent interactions. Often, however, this factor must be balanced against others, such as the cost of the process, the need for a specific support material, and ensuring that the substrates are not sterically hindered from diffusing to the active site of the immobilised enzyme in order to react at a sufficient rate.
The immobilised enzyme could have had more or less enzyme molecules than the free. A possible way round this method is to add the free enzyme to the Sodium Alginate as before, but instead of adding the mixture to the Calcium Chloride straight away, 2cm³ of the Amylase - Sodium alginate mix should be measured out, and then added to the Calcium Chloride. That way, an even 2cm³ of immobilised enzyme would have been added to the Starch, and 2cm³ of the free enzyme would have been added. This would then have been a fair test.
As enzymes are catalytic molecules they are not directly used up by the process in which they are used. However due to denaturation, they do loose activity with time. Therefore they should be stabilised against denaturation. When the enzymes are used in a soluble form they can contaminate the product, and its removal may involve extra purification costs. In order to eliminate wastage and improve productivity the enzyme and product can be separated during the reaction. The enzyme can be imprisoned allowing it to be reused but also preventing contamination of the product – this is known as immobilisation.
Unstable enzymes may be immobilised by being attached to or located within an insoluble support, therefore the enzyme is not free in solution. Once attached, an enzyme’s stability is increased, possibly because its ability to change shape is reduced.
Enzymes are proteins, and their function is determined by their complex structure. The reaction takes place in a small part of the enzyme
called the active site, while the rest of the protein acts as "scaffolding".