Factors that affect the respiration of immobilised yeast.

Pyruvic acid has to be broken down in respiration when formed by breaking down of glucose molecules, this can’t be done in the same way as it is aerobically when respiring anaerobically which is how the carbon dioxide and ethanol is formed through the zymase. Here is the equation for the aerobic respiration: -

Glucose + oxygen => energy + carbon-dioxide + ethanol

Yeast can also respire without oxygen but less energy will be released. Respiration without oxygen is known as anaerobic respiration. When yeast respires anaerobically it produces alcohol. The reaction has the following equation: -

Glucose => energy + alcohol + carbon-dioxide

Cells, such as yeast are often used in industrial processes. At the end of the process the yeast is often mixed up with the product and cannot be easily separated from it. Immobilization is a method, which traps the yeast cells in a bead, which can be more easily separated from the product. The method also means that it may be possible to reuse the yeast once it has been separated from the product. This method is often used in a continuous flow system.

To observe the respiration of yeast cells, a special blue coloured dye known as Resazurin dye is used. It changes colour when the yeast cells respire. The more respiring yeast there are (or the faster yeast cells are respiring) the faster the colour changes. Likewise the rate of respiration can be measured by the amount of carbon dioxide produced