Question

Given below are two statements:
• [Statement (I):] Saccharomyces cerevisiae, an yeast, is the most widely used microorganism for industrial ethanol fermentation. 
• [Statement (II):] Saccharomyces cerevisiae produces ethanol through glycolytic (Embden Meyerhoff Parnas) Pathway. 
In light of the above statements, choose the most appropriate answer from the options given below. 
 

• A. Both Statement (I) and Statement (II) are correct.
• B. Both Statement (I) and Statement (II) are incorrect.
• C. Statement (I) is correct but Statement (II) is incorrect.
• D. Statement (I) is incorrect but Statement (II) is correct.

Hint:

While S. cerevisiae is highly efficient at fermenting 6-carbon sugars (like glucose) via the EMP pathway, genetically engineered strains are used to ferment 5-carbon sugars (like xylose) for cellulosic ethanol production.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Industrial ethanol production relies on the fermentation of sugars by microorganisms under anaerobic conditions.
Yeast species have been optimized for high-yield fermentation and tolerance to ethanol.

Step 3: Detailed Explanation:
Let us evaluate both statements:
- Statement (I) is correct: The budding yeast Saccharomyces cerevisiae is the primary microorganism used for industrial bioethanol production and brewing.
It has a high rate of glycolysis, efficiently ferments hexose sugars (like glucose), and can tolerate high concentrations of both ethanol and osmotic stress.
- Statement (II) is correct: Saccharomyces cerevisiae breaks down glucose into pyruvate via the classic Embden-Meyerhof-Parnas (EMP) glycolytic pathway.
Under anaerobic conditions, pyruvate is converted to acetaldehyde by the enzyme pyruvate decarboxylase, releasing CO$_2$.
Acetaldehyde is then reduced to ethanol by alcohol dehydrogenase, regenerating NAD$^+$:
\[ \text{Glucose} \xrightarrow{\text{EMP Pathway}} 2\text{ Pyruvate} \rightarrow 2\text{ Acetaldehyde} \rightarrow 2\text{ Ethanol} + 2\text{CO}_2 \] Therefore, both statements are correct.

Step 4: Final Answer:
Both Statement (I) and Statement (II) are correct, matching Option (A).