Immobilised Enzymes

This lesson covers: 

1. What enzyme immobilisation is
2. The main methods of enzyme immobilisation
3. The advantages and disadvantages of using immobilised enzymes
4. Immobilising lactase to produce lactose-free milk

What is enzyme immobilisation?

Enzymes are crucial in various industries such as medicine, food technology, and industrial processing. However, they can be very expensive, which is why companies are finding ways to recycle and reuse enzymes.

One such method is enzyme immobilisation, which involves attaching or enclosing an enzyme onto a solid support or matrix. This allows for the reuse of the enzyme and increases its stability.

The main methods of enzyme immobilisation

There are a few different methods of immobilising enzymes.

Some of these methods of enzyme immobilisation are:

1. Binding - Enzymes may be bound to insoluble support materials like cellulose or collagen fibres by covalent or ionic bonds.
2. Adsorption - Enzymes may be adsorbed onto the surface of insoluble support materials.
3. Entrapment - Enzymes may be trapped in a matrix (e.g. silica gel) or a microcapsule.
4. Encapsulation - Enzymes may be isolated by a partially permeable membrane (e.g. within semi-permeable alginate beads).

The advantages and disadvantages of using immobilised enzymes

Using immobilised enzymes in industrial processes comes with both advantages and disadvantages. These are crucial for understanding their application and efficiency.

Advantages:

• Cost-effective - Immobilising enzymes allows for the reuse of enzymes, reducing the need to purchase new enzymes.
• Product purity - Immobilisation produces enzyme-free products, avoiding contamination of the product with the enzyme.
• Improved stability - Immobilised enzymes are more tolerant of temperature and pH changes than enzymes in solution, making them more stable and less likely to denature.

Disadvantages:

• Higher initial costs - Materials and bioreactors are more expensive than free enzymes and traditional fermenters, so are not always cost effective for small-scale production.
• Reduced enzyme activity - Immobilisation may reduce enzyme efficiency.
• Technical problems - The reactor systems are complex and prone to more technical problems.

Immobilising lactase to produce lactose-free milk

Milk contains lactose, a sugar that some people cannot properly digest. To create lactose-free milk, companies often remove lactose by immobilising the enzyme lactase, which breaks down lactose into glucose and galactose.

Here are the steps involved:

1. The lactase enzyme is attached to alginate beads to immobilise it.
2. The lactase-containing beads are packed into a column.
3. Milk is allowed to flow through the column.
4. Lactase hydrolyses the lactose in the milk into glucose and galactose, producing lactose-free milk.
5. The lactase remains in the column, allowing more milk to be processed continually.
6. The lactose-free milk can then be used to make dairy products for lactose-intolerant individuals.