Commercial Use of Enzymes

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

Immobilised Enzymes

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.

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

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

How a Biosensor Works

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