Question

Which microorganism is commonly used for industrial production of ethanol?

• A. Escherichia coli
• B. Bacillus subtilis
• C. Saccharomyces cerevisiae
• D. Lactobacillus

Hint:

The conversion of glucose to ethanol by yeast follows the stoichiometry: \(C_{6}H_{12}O_{6} \rightarrow 2C_{2}H_{5}OH + 2CO_{2}\).

Answer 1

The Correct Option is C

Step 1: Basic idea of ethanol production. 
Large-scale ethanol is produced by fermenting sugars such as glucose or molasses. This process is carried out in the absence of oxygen and requires a microorganism that can efficiently convert sugars into alcohol.

Step 2: Microorganism used in industry.
The yeast Saccharomyces cerevisiae is most widely used for ethanol fermentation in industries. It is preferred because:

• It converts sugars into ethanol very efficiently.
• It can survive and function even at high ethanol concentrations (about \(12\!-\!15\%\)).
• It grows well in acidic conditions, which helps prevent contamination by unwanted bacteria.

Other microorganisms are used for different purposes:

• Escherichia coli is mainly used in genetic and molecular research.
• Bacillus subtilis is employed for enzyme and antibiotic production.
• Lactobacillus is involved in lactic acid fermentation, such as yogurt production.

Step 3: Final conclusion.
The microorganism most commonly used worldwide for industrial ethanol production is Saccharomyces cerevisiae.