Immobilized enzymes

in 1897, the Buchner brothers showed that an extract of yeast, containing no yeast cells, would convert sucrose into alcohol
Louis Pasteur had claimed that fermentation of sugars to alcohol could only occur if living cells were present
- part of the vitalism theory (stated that substances in animals and plants can only be made under the influence of a "vital spirit" or "vital force")
  - the artificial synthesis of urea disproved this theory
the Buchners' research provided a clearer falsification of the theory
more than 500 enzymes now have commercial uses

the enzymes used in industry are usually immobilized
this is the attachment of the enzymes to another material or into aggregations so that the movement of the enzyme is restricted
there are many ways of doing this, such as
- attaching the enzymes into a glass surface
- trapping them in an alginate gel
- bonding them together to form enzyme aggregates
enzyme immobilization has several advantages:
- the enzyme can be easily separated from the products of the reaction, stopping the reaction at the ideal time and preventing contamination of the products
- after being retrieved from the enzyme mixture, the enzyme can be recycled, giving useful cost savings, especially as many enzymes are very expensive
- immobilization increases the stability of enzymes to changes in temperature and pH, reducing the rate at which they are degraded and have to be replaced
- substrates can be exposed to higher enzyme concentration than with dissolved enzymes, speeding up reaction rates