Answer:
Ethanol is prepared by the fermentation of sugar by the enzymes invertase and zymase.
What is fermentation?
Fermentation is an anaerobic process in which energy can be released from glucose even if oxygen is not available.
Types of fermentation
There are three different types of fermentation:
- Lactic Acid Fermentation – In this, starch or sugar is converted into lactic acid by yeast strains and bacteria. During exercise, energy expenditure is faster than the oxygen supplied to the muscle cells. This results in the formation of lactic acid and painful muscles.
- Alcohol Fermentation – Pyruvate, the end product of glycolysis is broken down into alcohol and carbon dioxide. Wine and beer are produced by alcoholic fermentation.
- Acetic Acid Fermentation – Starch and sugar present in grains and fruits ferment into vinegar and condiments. E.g. apple cider vinegar.
The yeast Saccharomyces cerevisiae generates the enzymes invertase and zymase, which are responsible for the alcoholic fermentation of sucrose. The fermentation medium is typically sugarcane molasses, which contains sucrose. This medium is used to grow yeast cells for anaerobic respiration, that produces ethanol and carbon dioxide.
\(\begin{array}{l}C_{12}H_{22}O_{11} + H_{2}O\overset{Invertase}{\rightarrow}C_{6}H_{12}O_{6}\end{array} \)
The enzyme zymase converts this mixture to ethanol.
\(\begin{array}{l}C_{6}H_{12}O_{6} \overset{Zymase}{\rightarrow}2C_{2}H_{5}OH + 2CO_{2}\end{array} \)
