(i) the uses of immobilised enzymes in biotechnology and the different…

The idea

Immobilised enzymes are catalysts fixed to a solid support or trapped in a matrix so they stay in place while substrate flows past. This lets a product be made continuously, allows the enzyme to be recovered and reused, and reduces contamination of the product. Uses in biotechnology include producing lactose-free milk by immobilised lactase, making glucose syrup from starch using immobilised amylase, and producing high-fructose syrup with immobilised glucose isomerase. Methods of immobilisation include adsorption onto an inert support such as clay, covalent bonding to a support, entrapment in a gel such as alginate, and encapsulation in a semi-permeable membrane or microcapsule. Each method trades enzyme leakage against reduced activity or diffusion limits.

What earns the marks

• States that immobilised enzymes are attached to a support or trapped in a matrix so they remain in place.
• Explains a benefit: enzyme can be recovered and reused, allowing continuous processing and reducing product contamination.
• Gives a named biotechnological use, such as immobilised lactase producing lactose-free milk.
• Gives another named use, such as immobilised amylase or glucose isomerase producing glucose or high-fructose syrup.
• Identifies a method of immobilisation, such as adsorption, covalent bonding, entrapment in alginate gel or encapsulation.
• Links a method to a limitation, such as enzyme leakage from adsorption or reduced substrate access in entrapment.

Common mistakes and how to put them right

• Confusing immobilisation with denaturation.

  Put it right: The enzyme is physically or chemically fixed, not destroyed, and retains catalytic activity.

• Assuming immobilised enzymes are used up in the reaction.

  Put it right: They are recovered and reused, which is the main advantage.

• Naming only one method when the question asks for different methods.

  Put it right: Distinguish adsorption, covalent bonding, entrapment and encapsulation.

Exam tips

• Read whether the question asks for a use, a method or a benefit, and answer that specific point.
• Use precise terminology such as adsorption, entrapment and encapsulation rather than vague words like 'trapped'.
• When a limitation is asked for, link it to the specific method, for example leakage from adsorption.