immobilised enzymes

• • Isolated enzymes used in industry can become mixed in with the products of a reaction.
  • The products then need to be separated from this mixture, which can be complicated and costly.
  • This is avoided in large-scale production by using immobilised enzymes - enzymes that are attached to an insoluble material so they can't become mixed with the products.
• ways to immobilise enzymes

  1. Enclosed in jelly-like alginate beads, which act as a semipermeable membrane.
  2. trapped in a silica gel matrix
  3. Covalently bonded to cellulose or collagen fibres
• • In industry, the substrate solution for a reaction is run through a column of immobilised enzymes.
  • The active sites of the enzymes are still available to catalyse the reaction but the solution flowing out of the column will only contain the desired product.
• advantages

  • Columns of immobilised enzymes can be washed and reused - this reduces the cost of running a reaction on an industrial scale because you don't have to keep buying new enzymes
  • The product isn't mixed with the enzymes - no money or time is spent separating them out.
  • Immobilised enzymes are more stable than free enzymes - they're less likely to denature (become inactive) in high temperatures or extremes of pH.
• disadvantages

  • Extra equipment is required, which can be expensive to buy.
  • Immobilised enzymes are more expensive to buy than free enzymes, so coupled with the equipment costs, they're not always economical for use in smaller-scale production.
  • The immobilisation of the enzymes can sometimes lead to a reduction in the enzyme activity because they can't freely mix with their substrate.
• Conversion of lactose to glucose and galactose

  • Some people are unable to digest lactose (a sugar found in milk) because they don't produce enough (or any) of the enzyme lactase.
  • Lactase breaks lactose down into glucose and galactose via a hydrolysis reaction.
  • Industrially, fresh milk can now be passed over immobilised lactase to produce lactose-free milk for use in the production of lactose-free dairy products.
• Production of semi-synthetic penicillins

  • Penicillin is a useful antibiotic, but some bacteria have become penicillin resistant.
  • Semi-synthetic penicillins can now be produced, which have the same antibiotic properties as natural penicillin, but are effective against penicillin-resistant organisms.
  • Immobilised penicillin acylase enzyme is used in their production.
• Conversion of dextrins to glucose

  • Glucose and glucose syrup are used in massive amounts in industry, e.g. they're used in the food industry to sweeten and thicken foods.
  • Glucose can be derived from starchy foods, such as corn and potatoes, with the help of immobilised enzymes.
  • Starch breaks down into dextrins (carbohydrate products), which are then broken down into glucose by the immobilised enzyme glucoamylase.
• Conversion of glucose to fructose

  • Fructose is a sugar that's much sweeter than glucose.
  • It's used as a sweetener in food - using fructose rather than glucose means that less sugar is needed to obtain the same level of sweetness in our foods.
  • Immobilised glucose isomerase is used to convert glucose to fructose on an industrial scale.
• Production of pure samples of L-amino acids

  • Amino acids have two chemical forms (isomers) - L or D
  • Most amino acids utilised by the body need to be in the L form.
  • Scientists are able to chemically synthesise amino acids, but end up with a mix of L and D forms.
  • The enzyme aminoacylase separates them.
  • Immobilised aminoacylase is used for the industrial production of pure samples of L-amino acids, which can be used for many purposes in the production of animal and human food, as well as in dietary supplements.
• Conversion of acrylonitrile to acrylamide

  • Acrylamide is a chemical that is typically used in industry to produce synthetic polymers (e.g. plastics), which have a wide range of uses.
  • For example, acrylamide is involved in the production of the polymer that's used in disposable nappies to make them super-absorbent.
  • In industry, immobilised nitrilase is used to convert acrylonitrile (a man-made chemical) to acrylamide.