Role of yeast in bioprocessing and foods In which of the following products is yeast the primary microorganism responsible for the fermentation process?

Introduction / Context:
Different fermented foods and industrial products rely on specific microbes. Recognizing the lead organism in each process is fundamental to bioprocess engineering and food microbiology.

Given Data / Assumptions:

• Yeasts (e.g., Saccharomyces spp.) are renowned ethanologens.
• Several listed foods are predominantly bacterial fermentations.

Concept / Approach:
Yeasts convert sugars to ethanol and carbon dioxide via glycolysis and alcoholic fermentation. In contrast, acetic acid (vinegar) is produced by acetic acid bacteria (Acetobacter/Komagataeibacter) through ethanol oxidation, and yogurt/curd primarily uses lactic acid bacteria (Lactobacillus/Lactococcus). Cheese relies on lactic cultures and ripening microbes; some cheeses may include yeasts adjunctively, but not as the primary fermenter broadly.

Step-by-Step Solution:

Verification / Alternative check:
Breweries, distilleries, and bioethanol plants use yeast starters or propagated yeast as the core biocatalyst.

Why Other Options Are Wrong:

• Acetic acid: produced by aerobic acetic acid bacteria using ethanol as substrate.
• Cheese/curd: driven by lactic acid bacteria; yeasts may play niche roles in ripening for some styles.
• Tempeh: primarily Rhizopus mold, not yeast.

Common Pitfalls:
Generalizing yeast involvement across all fermented foods; roles vary dramatically by product.

Final Answer:
Ethyl alcohol (beverages and fuel ethanol)