# Koji mould (Aspergillus oryzae)

**Aspergillus oryzae**

**Known today as.** The mould grown on steamed rice or soybeans.

Kind: Fungus

## What was it used for?

The starter of sake, soy sauce, and miso.

## What does modern science say?

A domesticated relative of the aflatoxin mould, which does not make the toxin.

## Pharmacognosy and toxicology

- **amylase**: 
- **protease**: 
- **kojic acid**: 

**Mechanism.** The enzymes of *Aspergillus oryzae* break down the starch of rice for sake and the protein of soy for miso and soy sauce; the domesticated mould carries the aflatoxin gene cluster of its wild relative *A. flavus* in a broken, silent form.

**Dose.** None; kojic acid, used in cosmetics to lighten skin, is restricted in cosmetics in the European Union.

**Standing.** Named the national fungus of Japan by the Brewing Society of Japan in 2006; listed as generally recognised as safe by the US Food and Drug Administration.

## What lore surrounds it?

The Brewing Society of Japan named it the national fungus in 2006.

## Sources

- Machida, M., et al. (2008). Genomics of *Aspergillus oryzae*. *DNA Research* 15: 173–183.
- Wikipedia contributors. “Aspergillus oryzae.” *Wikipedia, The Free Encyclopedia*. en.wikipedia.org/wiki/Aspergillus_oryzae (read 2 October 2026).
- Wikipedia contributors. “Kojic acid.” *Wikipedia, The Free Encyclopedia*. en.wikipedia.org/wiki/Kojic_acid (read 2 October 2026).
- Machida, M., et al. (2005). “Genome sequencing and analysis of *Aspergillus oryzae*.” *Nature* 438.

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*Koji mould.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-03. The Thinking Press. https://thethinkingpress.org/materia-medica/koji-mould

Historical description, not medical advice.