Question

The alcohol in Kefir is produced by _______________________

• A. Lactococcus lactis
• B. Lactobacillus brevis
• C. Leuconostoc spp.
• D. Saccharomyces delbrueckii

Hint:

Alcohol production in fermented milks (like Kefir and Kumiss) is always carried out by yeasts (like Saccharomyces or Kluyveromyces species) rather than lactic acid bacteria.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Kefir is a unique, fermented milk drink with a fizzy, slightly alcoholic taste. It is produced using Kefir grains, which consist of a symbiotic matrix of bacteria and yeasts.

Step 2: Detailed Explanation:
- The fermentation of Kefir involves both lactic acid fermentation (by bacteria) and alcoholic fermentation (by yeasts).
- While bacteria like Lactococcus lactis and Lactobacillus produce lactic acid, lactose-fermenting yeasts like {Saccharomyces delbrueckii (and Kluyveromyces marxianus) undergo anaerobic alcoholic fermentation.
- These yeasts convert sugars (glucose and galactose derived from lactose) into ethanol (alcohol) and carbon dioxide (\(\text{CO}_2\)), which gives Kefir its characteristic fizzy, carbonated, and slightly alcoholic profile.

Step 3: Final Answer
The alcohol in Kefir is produced by the yeast Saccharomyces delbrueckii.