1. Commercial Use of Enzymes

2. Immobilised Enzymes
These are enzyme molecules that are fixed, bound or trapped on an inert matrix such as a gel capsule, alginate beads.
There are four main methods available for immobilising enzymes:
a     Adsorption in glass or alginate beads – enzyme is attached to the outside of an inert material
b.    Cross-linkage to another chemical e.g. cellulose or glyceraldehydes.
c.     Entrapment in a silica gel – enzyme is held in a mesh or capsule of an inert material.
d.     Membrane confinement

3. Immobilised Enzymes

4. Advantages and Disadvantages of Using Immobilised Enzymes
Advanatages
Disadvantages
Easier to separate enzyme and products
The process of immobilizing the enzyme could distort the shape and reduce activity
Increases the stability of the enzyme – they are more tolerant to temperature and changes in pH
Enzyme could become detached
Several enzymes with differing pH and temp optima could be used together
Expensive to set up intially
Enzymes can be easily added or removed therefore offering a greater level of control over the reaction.

5. An Application of immobilized enzymes
Biosensors
Can be used for the rapid and accurate detection of minute traces of biologically important molecules. Used in medical diagnoses and environmental monitoring.
Biological
Sample Detection Transducer
Solution Element
Signal
Signal Processor
Readout

6. Examples of Biosensors
Work on the principle that enzymes are specific and able to select one type of molecule from a mixture even in very low concentrations
Molecule to be detected
Enzyme used in Biosensor
Glucose
Glucose oxidase
Urea
Urease
Cholesterol
Cholesterol oxidase
Alcohols
Alcohol oxidase
Penicillin
Penicillinase

7. How a Biosensor Works

8. Glucose Biosensor - Diabetics
Glucose diffuses from the the blood through the membrane to gel
Glucose oxidase acts upon the glucose and oxygen to produce gluconic acid
Amount of oxygen used is equivalent to the amount of glucose in the gel
Electrodes respond to changes in the oxygen tension
Size of electrical signal proportional to oxygen uptake and thus glucose concentration