Question

(a) What is fermentation? Give one example.
(b) Write the balanced chemical equations of the reactions taking place in the manufacture of ethyl alcohol from sugar.

Answer 1

(a)
Fermentation (a metabolic process) converts sugar to acids, gases, or alcohol. It is observed in yeast, bacteria, and in oxygen-starved muscle cells. An example is lactic acid fermentation.
(b)
Fermentation of sucrose with the enzyme invertase (present in yeast) gives a mixture of glucose and fructose.
$\underset{\text{Sucrose}}{C_{12}{H}_{22}{O}_{11}}+H_{2}O\stackrel{Invertase}{\to }\underset{\text{Glucose}}{C_6{H}_{12}{O}_6}+\underset{\text{fructose}}{C_6{H}_{12}{O}_6}$
This mixture is converted to ethanol by enzyme zymase.
$\underset{\text{Glucose or fructose}}{C_6{H}_{12}{O}_6}\stackrel{Zymase}{\to }\underset{\text{ethanol}}{2C_2{H}_{5}OH}+2C{O}_2$