Question

Which among the following are homofermentative lactic acid bacteria?
(A). Lactobacillus acidophilus
(B). Lactococcus lactis
(C). Leuconostoc mesenteroides
(D). Enterococcus faecalis
Choose the correct answer from the options given below:

• A. (A), (B) and (D) only.
• B. (A), (B) and (C) only.
• C. (A), (B), (C) and (D).
• D. (B), (C) and (D) only.

Hint:

Remember that the genus Leuconostoc is entirely heterofermentative, producing carbon dioxide and flavor compounds (diacetyl), which excludes option (C).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Lactic acid bacteria (LAB) are classified into homofermentative and heterofermentative categories based on their metabolic pathways for fermenting carbohydrates.

Step 2: Detailed Explanation:
Let us analyze the metabolic characteristics of the listed bacteria:

• Homofermentative LAB: These bacteria utilize the Embden-Meyerhof-Parnas (glycolytic) pathway to ferment hexose sugars, producing lactic acid as the sole or primary end-product (at least 90% of total metabolites). Examples include {Lactobacillus acidophilus, {Lactococcus lactis, and {Enterococcus faecalis.

• Heterofermentative LAB: These bacteria lack the aldolase enzyme and use the 6-phosphogluconate/phosphoketolase pathway to ferment sugars, producing lactic acid, carbon dioxide, ethanol, and acetic acid. A classic example is {Leuconostoc mesenteroides.
Therefore, (A), (B), and (D) are homofermentative, while (C) is heterofermentative.

Step 3: Final Answer
The homofermentative bacteria are (A), (B), and (D) only.