Question

Why are large quantities of ethanol produced with a relatively small yeast biomass during fermentation?

Answer 1

Ethanol is a renewable source of energy that can replace fossil fuels like oil, gas, and coal. It is produced by the process of fermentation as a part of anaerobic metabolic process in certain eukaryotes like yeasts and certain bacteria. Since it is an anaerobic process, it does not require oxygen.

Yeast or Saccharomyces cerevisiae is known to ferment glucose into ethanol in the absence of oxygen. It is a two-step process. In the first step, the yeast breaks down glucose molecules into 2 pyruvate molecules. These 2 pyruvate molecules are then converted to 2 molecules of carbon dioxide and 2 molecules of ethanol. ATP is also produced as a part of this process which is used by the yeast cells. The ethanol thus formed is distilled and purified for use.

A relatively small yeast biomass are able to produce large quantities of ethanol because of yeast's

• Ability to grow fast.
• Ability to efficiently utilize glucose
• Ability to tolerate wide range of pH, extremely low oxygen levels, and limited nutrients.

Rapid growth of yeast enables in the production high amount of ethanol. This is because right amount of glucose triggers the production of glycolytic enzymes which activates the growth of yeast as well as the fermentation process.