Question:
Which of the following is a facultatively heterofermentative Lactobacillus species
Which of the following is a facultatively heterofermentative Lactobacillus species
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Remember that Group II (facultative heterofermenters) can use both pathways: they act homofermentatively on hexose sugars but use heterofermentative pathways when fermenting pentoses.
Updated On: Jul 24, 2026
- Lactobacillus helveticus
- Limosilactobacillus fermentum
- Levilactobacillus brevis
- Lacticaseibacillus casei
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The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
Lactic acid bacteria are divided into three metabolic groups based on their glucose fermentation pathways: obligately homofermentative, facultatively heterofermentative, and obligately heterofermentative.
Detailed Explanation:
Let us analyze the three metabolic classifications of lactobacilli:
1. Obligately Homofermentative (Group I): Ferment hexoses to produce almost exclusively lactic acid via the EMP pathway. They lack the enzyme phosphoketolase and cannot ferment pentoses. Examples include Lactobacillus helveticus and L. acidophilus.
2. Facultatively Heterofermentative (Group II): Ferment hexoses to lactic acid via the EMP pathway, but can also ferment pentoses to lactic acid and acetic acid using the phosphoketolase pathway in the presence of pentose sugars. Examples include Lacticaseibacillus casei (formerly Lactobacillus casei), L. rhamnosus, and L. plantarum.
3. Obligately Heterofermentative (Group III): Ferment hexoses to produce lactic acid, ethanol/acetic acid, and carbon dioxide (\(\text{CO}_2\)) gas via the phosphoketolase pathway. Examples include Limosilactobacillus fermentum and Levilactobacillus brevis.
Therefore, Lacticaseibacillus casei is a facultatively heterofermentative species.
Final Answer:
Lacticaseibacillus casei is a facultatively heterofermentative species. Hence, the correct option is (D).
Lactic acid bacteria are divided into three metabolic groups based on their glucose fermentation pathways: obligately homofermentative, facultatively heterofermentative, and obligately heterofermentative.
Detailed Explanation:
Let us analyze the three metabolic classifications of lactobacilli:
1. Obligately Homofermentative (Group I): Ferment hexoses to produce almost exclusively lactic acid via the EMP pathway. They lack the enzyme phosphoketolase and cannot ferment pentoses. Examples include Lactobacillus helveticus and L. acidophilus.
2. Facultatively Heterofermentative (Group II): Ferment hexoses to lactic acid via the EMP pathway, but can also ferment pentoses to lactic acid and acetic acid using the phosphoketolase pathway in the presence of pentose sugars. Examples include Lacticaseibacillus casei (formerly Lactobacillus casei), L. rhamnosus, and L. plantarum.
3. Obligately Heterofermentative (Group III): Ferment hexoses to produce lactic acid, ethanol/acetic acid, and carbon dioxide (\(\text{CO}_2\)) gas via the phosphoketolase pathway. Examples include Limosilactobacillus fermentum and Levilactobacillus brevis.
Therefore, Lacticaseibacillus casei is a facultatively heterofermentative species.
Final Answer:
Lacticaseibacillus casei is a facultatively heterofermentative species. Hence, the correct option is (D).
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