Immobilised enzymes in biotechnology

In a nutshell

Immobilised enzymes can be used in industry to save money as they prevent the process of product extraction. They have many advantages that allow them to be exploited in industrial processes.

Immobilised enzymes

Definition

Immobilised enzymes are enzymes that are attached to an insoluble material. This prevents them from being mixed with the products during industrial processes, as often the extraction of products in a reaction can be costly and time-consuming. There are three main ways enzymes can be immobilised.

1.	Enzymes can be encapsulated inside alginate beads, these beads act as a semi-permeable membrane.	1. Alginate bead, 2. Enzymes.
2.	Enzymes can be trapped inside a silica gel matrix.	1. Silica get matrix, 2. Enzymes.
3.	Enzymes can be covalently bonded to cellulose or collagen fibres.	1. Enzymes, 2. Cellulose or collagen fibres.

Immobilised enzyme column

Biology; Cloning and biotechnology; KS5 Year 12; Immobilised enzymes in biotechnology — 1. Substrate solution, 2. Column, 3. Enzymes immobilised in alginate, 4. Solution flowing out of the column.

The substrate solution is run through a column of immobilised enzymes. Here, the active sites of the enzymes are available to catalyse the reaction but only the product will flow out of the column.

Advantages and disadvantages of immobilised enzymes

Advantages	Disadvantages
These columns can be washed and reused, which reduces costs.	These columns require extra equipment which can be expensive.
No money or time is spent on separating enzymes and products.	Immobilised enzymes are more expensive than free enzymes so overall costs may not be reduced.
Immobilised enzymes are more stable than free enzymes. They are much less likely to denature at high temperatures or extreme pHs.	Immobilisation may lead to a reduction in enzyme activity as enzymes and substrates are not able to freely mix.

Immobilised enzymes in industry

Immobilised enzyme	Use	Description
Lactase	Conversion of lactose to glucose and galactose.	Some people cannot digest lactose and are therefore lactose intolerant. Fresh milk can be passed over lactase to produce lactose-free milk that can be consumed by these people.
Penicillin acylase	Production of semi-synthetic penicillins.	Some bacteria have become resistant to the antibiotic penicillin. Semi-synthetic penicillins are now produced to overcome this resistance and they are produced using penicillin acylase.
Glucoamylase	Conversion of dextrins to glucose.	Glucose and glucose syrup are widely used in the food industry to sweeten and thicken food. Glucose can be derived from starchy foods as starch breaks down into dextrins. Dextrins can be broken down into glucose by glucoamylase.
Glucose isomerase	Conversion of glucose to fructose.	Fructose is a sugar that is used as a sweetener in foods. Using glucose isomerase, glucose can be converted into fructose on an industrial scale.
Aminoacylase	Production of pure samples of L-amino acids.	Amino acids have two isomers known as L and D. Normally, for amino acids to be used by the body they have to be in their L form. Aminoacylase can be used to obtain pure samples of L-amino acids that can be added to food or dietary supplements.
Nitrile hydratase	Converts nitriles to amides.	This includes the conversion of acrylonitrile into acrylamide. Polyacrylamide is a plastic used as a thickener, in water treatment and paper-making as well as in the gel for electrophoresis.