Chapter 2.4 - Industrial Enzymes Flashcards
Why are enzymes useful in industrial processes?
They can catalyse reactions between particular chemicals no matter how big the culture
Most enzymes function well at quite low temperatures
What is an enzyme
Enzymes are biological catalysts for metabolic reactions either anabolic or catabolic
What is downstream processing?
The extraction of a particular enzyme from a fermentation mixture
What are the advantages of immobilising enzymes
Enzymes are not present with products so purification and downstream processing costs are kept to a minimum
Enzymes are immediately available for reuse, particularly useful for continuous cultures
Immobilised enzymes are more stable because the immobilising matrix protects the enzyme molecules.
What are the disadvantages of immobilising enzymes?
Immobilisation requires additional time, equipment and materials and so is more expensive to set up
Immobilised enzymes can be less active because they do not mix freely with the substrates
Any contamination is costly to deal with because the whole system would need to be stopped.
What are the four methods of immobilising enzymes?
Adsorption
Covalent bonding
Entrapment
Membrane separation
Explain how adsorption immobilises enzymes
The target enzymes mix with the immobility support material and bind to it due to a combination of hydrophobic interactions and ionic links.
Adsorption agents include clay, resin and glass beads.
Because the binding forces are not particularly strong, enzymes can become detached (known as leakage). However providing that enzyme molecules are held so that their actor site is not changed and is displayed adsorption still gives very high recto on rates.
Explain how covalent bonding causes immobilised enzymes
Enzymes can form covalent bonds with the support particle as well as each other using a cross-linking agent.
This method does not immobilise a huge amount of enzymes but the binding is very strong as covalent bonds are very strong so the amount of leakage is kept to a minimum
How does entrapment immobilise enzymes
Enzymes may be trapped in a gel bead in their natural state (ie are not bound to another molecule so their active sites stay in tact).
However reactions rates can be reduced evacuee whatever the trapping barrier is must be penetrated by the substrate. This means the active site of the enzyme is less easily available than it is with adsorbed or covalent bonded enzymes
How does membrane separation immobilise enzymes?
Enzymes may he physically separated from the substrate mixture by a partially permeable membrane.
The enzyme solution is held on one side of the membrane whilst the substrate solution passes along the other side.
Substrate molecules are small enough to pass through the membrane and the products formed can also pass back across the membrane but the enzymes are too big to fit through the membrane so stay enclosed.
