Immobilised Enzymes in Biotechnology
- An immobilised enzyme is an enzyme that is attached to an insoluble material to prevent mixing with the product
- Enzymes can be immobilised in several ways:
- Attached to an inert substance
- Enclosed in a capsule
- Contained within a partially permeable membrane
Different ways in which enzymes can be immobilised
- Enzymes are often immobilised for use in industrial processes as it means the enzyme can be reused in future processes rather than being discarded after it has been used once
- Reusing the enzyme also avoids the need to separate the enzyme from the product in downstream processing
- The immobilised enzymes are contained within a column through which the substrate is filtered 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 (enzymes are expensive)
- Immobilised enzymes have a greater tolerance of temperature and pH changes (immobilisation often makes enzymes 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 freely mix with the substrate
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
- Semi-synthetic penicillin which overcomes issues of penicillin resistance
- Enzyme: Penicillin acylase
- Converts the original form of penicillin into one which is effective against penicillin-resistant organisms
- Glucose products used to sweeten and thicken foods
- Enzyme: Glucoamylase
- Converts starch and other dextrins into glucose
- Fructose for sweetening of foods where a lower quantity of sugar is necessary
- Enzyme: Glucose isomerase
- Converts glucose into the sweeter sugar, fructose
- Purified samples of L-amino acids used in food production
- Enzyme: Aminoacylase
- Separates out L-amino acids from D-amino acids
- Acrylamide required in disposable nappy production
- Enzyme: Nitrilase
- Converts acrylonitrile into acrylamide
- Lactose-free dairy products such as milk
A closer look at lactose-free milk production
- Milk is a valuable source of nutrients containing protein, fat and the carbohydrate lactose
- 5-10% of the UK population are lactose intolerant
- Lactose is a disaccharide that is broken down into glucose and galactose
Using immobilised enzyme to modify milk
Examiner Tip
You will not necessarily be asked about these specific examples of industrial uses of immobilised enzymes, 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.
