|A. oryzae growing on rice to make koji|
(Ahlburg) E. Cohn
Aspergillus oryzae (Chinese: 麴菌, 麴霉菌, 曲霉菌, pinyin: qū meí jūn; Japanese: 麹, kōji, or 麹菌, kōji-kin, Korean: 누룩균, nurukgyun or 누룩곰팡이 nuruk-gompang-i) is a filamentous fungus (a mold). It is used in Chinese, Korean, and Japanese cuisine to ferment soybeans. It is also used to saccharify rice, other grains, and potatoes in the making of alcoholic beverages such as huangjiu, sake, makgeolli and shōchū. The domestication of A. oryzae occurred at least 2000 years ago. A. oryzae is used for the production of rice vinegars.
Dr. Eiji Ichishima of Tohoku University called the kōji fungus a "national fungus" (kokkin) in the journal of the Brewing Society of Japan, because of its importance not only for making the koji for sake brewing, but also for making the koji for miso, soy sauce and a range of other traditional Japanese foods. His proposal was approved at the society's annual meeting in 2006.
"Red kōji-kin" is a separate species, Monascus purpureus.
History of koji
300 BCE – A. oryzae (qu, pronounced "chew") is first mentioned in the Zhouli (Rites of the Zhou dynasty) in China. Its development is a milestone in Chinese food technology, for it provides the conceptual framework for three major fermented soy foods: soy sauce, jiang / miso, and fermented black soybeans, not to mention grain-based wines (including Japanese sake) and li (the Chinese forerunner of Japanese amazake).
Properties desirable in sake brewing and testing
The following properties of A. oryzae strains are important in rice saccharification for sake brewing:
- Growth: rapid mycelial growth on and into the rice kernels
- Enzymes: strong secretion of amylases (α-amylase and glucoamylase); some carboxypeptidase; low tyrosinase
- Aesthetics: pleasant fragrance; accumulation of flavoring compounds
- Color: low production of deferriferrichrome (a siderophore), flavins, and other colored substances
Initially kept secret, the A. oryzae genome was released by a consortium of Japanese biotechnology companies in late 2005. The eight chromosomes together comprise 37 million base pairs and 12 thousand predicted genes. The genome of A. oryzae is thus one-third larger than that of two related Aspergillus species, the genetics model organism A. nidulans and the potentially dangerous A. fumigatus. Many of the extra genes present in A. oryzae are predicted to be involved in secondary metabolism. The sequenced strain isolated in 1950 is called RIB40 or ATCC 42149; its morphology, growth, and enzyme production are typical of strains used for sake brewing.
Use in biotechnology
A. oryzae is a supporting character (of sorts) in the manga series Moyasimon: Tales of Agriculture and its anime adaptation.
- Index Fungorum
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