Manufacture of Ethanol from Molasses

Preparation of Ethanol (Drinking Alcohol)

Ethanol is the most important member of the alcohol series. Ethanol is prepared industrially by the fermentation of sugars in molasses, sugarcane or fruits such as grapes or starch obtained from various grains. Fermentation is the oldest method of making ethanol from sugars. It is the slow decomposition of complex organic compounds into simple compounds by the action of biological catalysts called enzymes.

Manufacture of Ethanol from Molasses

Molasses is the mother liquor left behind after the crystallization of sugar from sugarcane juice. It contains about 40% non-crystallizable sugar.
Mollasses is first diluted to about 10% concentration of sugar. Then, calculated amount of yeast is added and kept at an optimum temperature of about 305K. Yeast provides the enzymes invertase and Zymase which can cause fermentation. The enzyme invertase catalyses the hydrolysis of sugar into glucose and fructose. Glucose and fructose are decomposed into ethanol in the presence of the enzyme zymase. Ultimately, a dilute solution of ethanol (8-10%), called 'wash' is obtained.

Chemical Equations

C₁₂H₂₂O₁₁ + H₂O ------invertase------> C₆H₁₂O₆ (glucose) + C₆H₁₂O₆ (fructose)


C₆H₁₂O₆ (glucose / fructose) -----zymase-----> 2C₂H₅ - OH (ethanol) + 2CO₂