Traditional sake production employs a saccharifying mold and a fermenting yeast. Which organism listed is used as the koji mold to prepare sake?

Introduction / Context:
Sake brewing is a parallel fermentation: the mold breaks starch into sugars while yeast simultaneously ferments those sugars to alcohol. Identifying the correct saccharifying microorganism is core knowledge in fermented food microbiology.

Given Data / Assumptions:

• Koji preparation inoculates steamed rice with a mold.
• The mold must secrete amylases and proteases.

Concept / Approach:
Aspergillus oryzae, the koji mold, produces powerful amylases and proteases that convert rice starch into fermentable sugars and liberate amino acids, enabling robust yeast fermentation by sake yeast strains (Saccharomyces cerevisiae var. sake). Other listed microbes are not the standard koji mold for sake.

Step-by-Step Solution:

Verification / Alternative check:
Traditional and industrial sake methods consistently reference A. oryzae for koji production.

Why Other Options Are Wrong:

• Rhizopus/Lactobacillus: used in other fermentations, not standard for sake koji.
• Saccharomyces pyriformis: yeast name not used for standard sake production.
• Penicillium roqueforti: cheese ripening mold, not used in sake.

Common Pitfalls:
Confusing the saccharifying mold with the fermenting yeast; both are required but perform different roles.

Final Answer:
Aspergillus oryzae (koji mold)