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The alteration of natural biomolecules using science and engineering to provide good and services.

Biomolecule - a substance made by living organisms.

Most changes to food are caused by microorganisms - bacteria and microscopic fungi.

These produce enzymes that change molecules in the original substance into different molecules.

  • bacteria acts on a protein called casein in mile when it turns to cheese
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Fermenters are big steel vessels, in which microorganisms are grown.

Inside they are provided with exactly the right conditions to encourage them to grown and produce the substances we require.

  • Penicillium is used to produce penicillin

Before the microorganism is put into the fermenter it must be sterilised using high pressue steam to kill any miccroorganisms that might grow instead and cause competition for nutrients etc

Everything added to the fermenter is also sterilised

This is aseptic precautions

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Optimum conditions

These are supplied so that the most product possible is produced in the shortest time

  • nutrients - includes sources of carbs and nitrogen such as sugar and ammonium ions
  • optimum temperature - enzymes in the microorganism can work at a fast rate but don't get denatured
  • optimum pH - allow the enzymes to work efficiently
  • Oxygen - provided by bubbling sterile air into the fermenter so the microorganism can respire aerobically
  • Agitation - profuced by a stirrer to mix the oxygen and nutrients into all of the liquid
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