Immobilised Enzymes Flashcards
What are immobilised enzymes?
-enzymes that are attached to an insoluble material so they can’t become mixed with the products
How are enzymes immobilised using the entrapment in a matrix method, and what are the advantages and disadvantages of this method?
-the placement of an enzyme within the framework of a membrane or polymer matrix
-advantages= widely applicable to different processes
-disadvantages= may be expensive, difficult to entrap, diffusion of substrate to and product from the active site can be slow and hole up the reaction
How are enzymes immobilised using the surface immobilisation method, and what are the advantages and disadvantages of this method?
-covalent bonding to inorganic carriers e.g carries with amino, hydroxyl, carboxyl groups
-advantages = cost varies, enzymes strongly bound therefore unlikely to be lost, enzymes very accessible to substrate, pH and substrate concentration often have little effect on enzyme activity
-disadvantages = cost varies, active site of the enzyme may be modified in process making it less effective
How are enzymes immobilised using the membrane separation method, and what are the advantages and disadvantages of this method?
-adsorption to inorganic carriers e.g cellulose, silica, carbon nanotubes, and polyacrylamide gel
-advantages = simple and cheap to do, can be used with many different processes, enzymes very accessible to substrate and their activity is virtually unchanged
-disadvantages = enzymes can be lost from matrix relatively easily
What are the advantages of using immobilised enzymes in general?
-can be reused which is cheaper
-easily separated from the product of the reaction so reduced downstream processing is needed, therefore cheaper
-more reliable- there is a high degree of control over the process as the insoluble support provides a stable micro environment for the immobilised enzymes
-greater temperature tolerance-less easily denatured by heat and work at optimum levels over a much wider range of temperatures, making bioreactor less expensive to run
-easy to manipulate- catalytic properties can be altered to fit a particular process more easily than those of free enzymes
What are the disadvantages of using immobilised enzymes in general?
-reduced efficiency- process of immobilising may reduce its activity rate
-higher initial costs of material- more expensive than free enzymes, however don’t need to be replaces as frequently
-higher initial costs of bioreactor- system needed to use immobilised enzymes is different from traditional fermenters so there is an initial investment cost
-more technical issues- reactors which use immobilised enzymes are more complex then simple fermenters and so higher chance of something going wrong
Describe some examples of how immobilised enzymes are actually used
1) immobilised lactase is used to make lactose-free milk for people and animals who are intolerant. Immobilised lactase hydrolyses lactose to glucose and galactose, giving lactose free milk
2) immobilised aminoacylase is used to produce pure samples of L-amino acids used in the production of pharmaceuticals, cosmetics and food
3) immobilised glucose isomerase is used to produce fructose from glucose. Fructose is much sweeter than sucrose or glucose so is used as a sweetener in the food industries. Glucose isomerise is used to turn cheap glucose into very marketable fructose
4) immobilised glucoamylase is used to complete the breakdown of starch to glucose syrup. Amylase enzymes break starch down into shorter chain polymers called dextrins. The final breakdown of dextrins to glucose is catalysed by immobilised glucoamylase.
What is a biosensor? And how are immobilised enzymes used?
-biosensor use biological components to determine the presence and concentration of molecules such as glucose
-molecular recognition= a protein or ssDNA is immobilised to a surface. This will interact or bind to the specific molecule being investigated
-transduction= this interaction will cause a change in the transducer, which detects changes for example in pH and produced a response such as the release of an immobilised dye on a test strip
-display= this then produces a visible, qualitative or quantitative signal such as particular colour on strip or reading on test machine
