Question

……. are osmophilic yeasts.

• A. Saccharomyces Lactis
• B. Saccharomyces rouxii
• C. Saccharomyces Mellis
• D. Both 2 & 3

Hint:

Osmophilic = "Sugar loving." If you see high sugar or honey mentioned, look for Zygosaccharomyces or these specific Saccharomyces species. They cause "bursting" of jars through gas production.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The term "osmophilic" refers to organisms that can grow in environments with high osmotic pressure, specifically high sugar concentrations. The question asks which yeast species belong to this category.

Step 2: Detailed Explanation:

• Osmophilic Yeasts: These are a specialized group of yeasts that thrive in products like honey, concentrated fruit juices, jams, and maple syrup, where the water activity ($a_w$) is very low due to dissolved sugars.

• Saccharomyces rouxii (now Zygosaccharomyces rouxii): This is the most famous osmophilic yeast. it is used in the fermentation of soy sauce and miso but is also a major spoilage agent in high-sugar products. It can grow at sugar concentrations that would inhibit almost all other microbes.

• Saccharomyces mellis (now Zygosaccharomyces mellis): As the name suggests ("mellis" means honey), this yeast is frequently isolated from fermenting honey. It is specifically adapted to high osmotic environments.

• Saccharomyces lactis: This is a lactose-fermenting yeast (now Kluyveromyces lactis) primarily found in dairy products. While it tolerates some salts, it is not categorized as a primary osmophile compared to the other two.

Step 3: Final Answer:
Both S. rouxii and S. mellis are classical examples of osmophilic yeasts.