Supporting the growth of Yeast Cultures

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Janisha Patel

Biology Investigation

Supporting the Growth of Yeast Cultures with Different Carbon Sources

Aim: To investigate the difference in growth rates between yeast cultures that have been grown in different carbon sources.

Introduction: An investigation in being carried out to see whether the support of different carbon sources have an adverse effect on the growth rate of yeast cultures. Carbon sources are used to provide carbon as a macronutrient to micro-organisms to enable them to grow and reproduce rapidly. Carbon is often provided in the form of organic substances including glucose, organic acids, fatty acids or amino acids, for example photoautotrophic microorganisms such as Chlorella use carbon dioxide as their carbon source, which in affect supports their growth. Yeast, a single celled living microorganism is a type of fungi that also needs nutrition to enable it to reproduce efficiently. Therefore, the purpose of this experiment is to investigate which carbon source enhances the growth of yeast over a set period of time.

Materials/Apparatus

  • Conical flasks were used to mix the yeast, water and other compounds to produce a yeast culture whilst avoiding any spillages.
  • Measuring cylinders were used to measure the correct amounts of distilled water for the yeast culture.
  • An incubator was used to place the yeast culture in and increase the pressure to kill any unwanted micro-organisms.
  • Cotton wool was used to make a bung to place at the neck of the conical flask to prevent any impurities from entering the flask.
  • Foil was used to cover the neck of the conical flask to further protect the yeast culture from impurities entering.
  • Galactose was used as a carbon source.
  • Lactose was used as a carbon source.
  • Sucrose was used as a carbon source.
  • Glucose was used as a carbon source.
  • Maltose was used as a carbon source.
  • Fructose was used as a carbon source.
  • Ammonium sulphate was used to provide sulphur to the culture as it is an essential compound for the yeast to be able to grow.
  • Ammonium phosphate was used to provide phosphorus and nitrogen to the culture as they are essential elements for the yeast to be able to grow.
  • Measuring boats to measure out the ammonium compounds.
  • Scale to measure the ammonium compounds.
  • Autoclave tape to tape the foil to the conical flask.
  • Pipettes to place the yeast culture into cuvettes.
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Method:

Firstly, measure 100mls of distilled water in a measuring cylinder and place it in a clean conical flask. Measure 0.5g of ammonium phosphate and add it to the flask. Also measure 0.5g of ammonium sulphate and add it to the solution. Make the solution up to 200mls with distilled water. Label this conical flask as the ‘control’. Make a bung out of cotton wool and place it at the neck of the conical flask. Then cover the top of the conical flask with aluminium foil ensuring that it is not too ...

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