Immobilised Enzymes
Immobilised enzymes are widely used in industry
- Just before 1900, it was discovered that enzymes could be used to catalyse production of alcohol in the absence of yeast cell
- Since then, hundreds of enzymes have been developed outside of living cells for commercial purposes
- Uses of enzymes in industrial processes can be expensive, so we need ways to reuse them in order to be cost-effective
- An immobilised enzyme is an enzyme that is attached to an insoluble material to prevent mixing with the product and through this method, the enzyme can be reused in subsequent reactions
- Immobilised enzymes are used in the following commercial processes
- Agriculture
- Biosensors (diagnosis, analysis eg. for impurities)
- Manufacturing processes
- Energy generation
- Environmental management
- Food/drinks industry
- Medicines
- Attachment to an inert substance eg. glass
- Entrapment within a matrix e.g. alginate gel
- Entrapment within a partially permeable membrane
Different ways in which enzymes can be immobilised
- The mechanism of immobilised enzyme use works as follows:
- The immobilised enzymes are contained within a column
- The substrate is filtered through this column in solution
- As the substrate runs through the column, enzyme-substrate complexes are formed and products are produced
- These products then flow out of the column, leaving the enzymes behind to catalyse the reaction again
The immobilised enzymes are contained within a column
Advantages of immobilised enzymes
- There is no enzyme in the product (the product is uncontaminated) and therefore there is no need to further process or filter the end product
- The immobilised enzyme can be reused multiple times which is both efficient and cost-effective (many enzymes are expensive)
- Reusing the enzyme also avoids the need to separate the enzyme from the product in downstream processing
- Immobilised enzymes have a greater tolerance of temperature and pH changes (immobilisation often makes enzymes more stable)
- Substrates can be exposed to higher enzyme concentrations than when using enzymes in solution, increasing the rate of throughput
- Conditions can be controlled carefully, allowing immobilised enzymes to function close to their optimum conditions and be more stable
Disadvantages of immobilised enzymes
- Specialist expensive equipment is required
- Immobilised enzymes are more costly to buy, so are unlikely to be financially worthwhile for smaller industries
- The rate of reaction is sometimes lower when using immobilised enzymes as the enzymes cannot mix freely with the substrate
Examples of immobilised enzymes in industry
- There are many industrial and medical applications of immobilised enzymes, including production of the following:
- Lactose-free dairy products such as milk
- Enzyme: Lactase
- Converts lactose to glucose and galactose
- Lactose-free dairy products such as milk
- Enzyme: Penicillin acylase
- Converts the original form of penicillin into one which is effective against penicillin-resistant organisms
- Enzyme: Glucoamylase
- Converts starch and other dextrins into glucose
- Enzyme: Glucose isomerase
- Converts glucose into the sweeter sugar, fructose
- Enzyme: Aminoacylase
- Separates out L-amino acids from D-amino acids
- Enzyme: Nitrilase
- Converts acrylonitrile into acrylamide
Exam Tip
You will not necessarily be asked about these specific examples of industrial uses of immobilised enzymes (except for lactose modification), but it is useful to know of some uses in order to be able to apply your knowledge accurately in the exam.When discussing the advantages and disadvantages of immobilised enzymes, try to be specific about the cost implications as there are various considerations when it comes to the economical value of immobilising the enzymes.
