Question

Describe the industrial method of preparation of ethyl alcohol from starch. Give chemical equations of reactions also.

Answer 1

Hint: In industries, the starch is converted into ethyl alcohol by using some specific enzymes and this process is called fermentation. The starch is first degraded into its simpler form and then glucose is converted to ethyl alcohol by using some specific enzyme. One can write a chemical reaction also for this process.

Complete step by step answer:
1) First of all we will learn what starch is and how it can produce ethyl alcohol as a product. Starch is a type of carbohydrate that has a chemical formula ${C_6}{H_{10}}{O_5}$. Starch is generally found in food such as potato, maize, rice, etc.
2) The starch is generally extracted from the potato which is a very rich source of starch. The process of preparation of ethyl alcohol from starch is done by the fermentation process by using some specific enzymes. The first step in this process is the extraction of starch from the potato.
3) The extraction of starch from potato: The potato is crushed which is a very rich source of starch and then it is steamed at very high temperature and under pressure which will result in the formation of starch solution.
4) In the next step the starch is undergone through the hydrolysis process which will give the product as maltose. The enzyme used for this process is diastase. The reaction for this process is as below,
$2\left( {{C_6}{H_{10}}{O_5}} \right) + n{H_2}O\xrightarrow{{Diastase}}n\left( {{C_{12}}{H_{22}}{O_{11}}} \right)$
In the above reaction, the starch is converted into maltose by the hydrolysis process.
5) Now the last step is fermentation where the yeast is added to maltose which will be converted to glucose as below,
${C_{12}}{H_{22}}{O_{11}} + {H_2}O\xrightarrow{{Yeast}}2{C_6}{H_{12}}{O_6}$
Now the glucose formed is converted to ethyl alcohol by using the enzyme zymase as below,
${C_6}{H_{12}}{O_6}\xrightarrow{{Zymase}}{C_2}{H_5}OH + 2C{O_2}$
6) Hence, in the last step ethyl alcohol is formed as a product.

Note:
The starch solution which is prepared is also called Mash. Ethyl alcohol is also prepared by other methods of fermentation of molasses. Molasses is a leftover product in sugarcane production and also has about ${\text{60\% }}$ fermentable sugar which can be converted to ethyl alcohol.