Aspergillus oryzae

''Aspergillus oryzae'', also known as , is a filamentous fungus (a mold) used in East Asia to saccharify rice, sweet potato, and barley in the making of alcoholic beverages such as ''sake'' and '' shōchū'', and also to ferment soybeans for making soy sauce and ''miso''. However, in the production of fermented foods of soybeans such as soy sauce and ''miso'', '' Aspergillus sojae'' is sometimes used instead of ''A. oryzae''. Incidentally, in China and Korea, the fungi used for fermented foods for a long time in the production of traditional alcoholic beverages were not ''A. oryzae'' but fungi belonging to ''Rhizopus'' and ''Mucor''. '' A. oryzae'' is also used for the production of rice vinegars. Barley ''kōji'' (麦麹) or rice ''kōji'' (米麹) are made by fermenting the grains with ''A. oryzae'' hyphae.

Genomic analysis has led some scholars to believe that the Japanese domesticated the ''Aspergillus flavus'' that had mutated and ceased to produce toxic aflatoxins, giving rise to ''A. oryzae''.
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 ''kōji'' for ''sake'' brewing, but also for making the ''kōji'' for ''miso'', soy sauce, and a range of other traditional Japanese foods. His proposal was approved at the society's annual meeting in 2006.

The Japanese word ''kōji'' (麹) is used in several meanings, and in some cases it specifically refers to ''A. oryzae'' and ''A. sojae'', while in other cases it refers to all molds used in fermented foods, including ''Monascus purpureus'' and other molds, so care should be taken to avoid confusion.

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

Varieties used for ''shōchū'' making

Three varieties of kōji mold are used for making '' shōchū'', each with distinct characteristics. (Japanese) (Japanese)

Genichirō Kawachi (1883 -1948), who is said to be the father of modern ''shōchū'' and Tamaki Inui (1873 -1946), a lecturer at University of Tokyo succeeded in the first isolation and culturing of ''aspergillus'' species such as ''A. kawachii'', ''A. awamori'', and a variety of subtaxa of ''A. oryzae'', which let to great progress in producing ''shōchū'' in Japan. Since then, ''aspergillus'' developed by Kawachi has also been used for ''soju'' and ''makgeolli'' in Korea.初代 河内源一郎（1883～1948）
Kawauchi-kin honpo

* Yellow ''kōji'' (''A. oryzae'' etc.) is used to produce ''sake'', and at one time all ''honkaku shōchū''. However, yellow ''kōji'' is extremely sensitive to temperature; its ''moromi'' can easily sour during fermentation. This makes it difficult to use in warmer regions such as Kyūshū, and gradually black and white ''kōji'' became more common in production of ''shōchū''. Its strength is that it gives rise to a rich, fruity, refreshing taste, so despite the difficulties and great skill required, it is still used by some manufacturers. It is popular amongst young people who previously had no interest in typically strong potato ''shōchū'', playing a role in its recent revival. Thus, white and black ''kōji'' are mainly used in the production of ''shōchū'', but only yellow ''kōji'' (''A. oryzae'') is usually used in the production of ''sake''.
* White ''kōji'' (''A. kawachii'' etc.) was discovered as a mutation from black ''kōji'' by Genichirō Kawachi in 1923. This effect was researched and white ''kōji'' was successfully grown independently. White ''kōji'' is easy to cultivate and its enzymes promote rapid saccharization; as a result, it is used to produce most ''shōchū'' today. It gives rise to a drink with a refreshing, mild, sweet taste.
* Black ''kōji'' ('' A. awamori'' also known as ''A. luchuensis'' etc.) is mainly used to produce ''shōchū'' and ''awamori''. In 1901, Tamaki Inui, lecturer at University of Tokyo succeeded in the first isolating and culturing. In 1910, Genichirō Kawachi succeeded for the first time in culturing var. kawachi, a variety of subtaxa of ''A. awamori''. This improved the efficiency of shōchū production. It produces plenty of citric acid which helps to prevent the souring of the '' moromi''. Of all three ''kōji'', it most effectively extracts the taste and character of the base ingredients, giving its ''shōchū'' a rich aroma with a slightly sweet, mellow taste. Its spores disperse easily, covering production facilities and workers' clothes in a layer of black. Such issues led to it falling out of favour, but due to the development of new ''kuro-kōji'' (NK-''kōji'') in the mid-1980s, interest in black ''kōji'' resurged amongst ''honkaku shōchū'' makers because of the depth and quality of the taste it produced. Several popular brands now explicitly state they use black ''kōji'' on their labels.

Genome

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

Trans-resveratrol can be efficiently cleaved from its glucoside piceid through the process of fermentation by ''A. oryzae''.

Secondary metabolites

''A. oryzae'' is a good choice as a secondary metabolite factory because of its relatively few endogenous secondary metabolites. Transformed types can produce: polyketide synthase-derived 1,3,6,8-tetrahydroxynaphthalene, alternapyrone, and 3-methylorcinaldehyde; citrinin; terrequinone A; tennelin, pyripyropene, aphidicolin, terretonin, and andrastin A by plasmid insertion; paxilline and aflatrem by co-transformation; and aspyridone, originally from ''A. nidulans'', by Gateway cloning.

History of ''kōji'' in a broad sense

''麹'' (Chinese ''qū'', Japanese ''kōji'') which means mold used in fermented foods, was first mentioned in the ''Zhouli'' ( Rites of the Zhou dynasty) in China in 300 BCE. 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 ''douchi'', not to mention grain-based wines (including Japanese ''sake'' and Chinese ''huangjiu'') and ''li'' (the Chinese forerunner of Japanese ''amazake'').Shurtleff, W.; Aoyagi, A.
History of Koji - Grains and/or Soybeans Enrobed with a Mold Culture (300 BCE to 2012).
' Lafayette, California: Soyinfo Center. 660 pp. (1,560 references; 142 photos and illustrations, Free online)

Gallery

File:Aspergillus_oryzae.jpg, Conidiophores with conidia of the microscopic fungus ''A. oryzae'' under light microscope
File:Four 3-day old Aspergillus colonies on a Petri dish.png, Four ''Aspergillus'' colonies grown at 37 °C for three days on rich media: The bottom two are ''A. oryzae'' strains.

See also

References

External links

Making Rice Koji from Koji Spores''Aspergillus oryzae'' genome
from the Database of Genomes Analysed a
NITE

Global Aspergillus oryzae Market Report 2020 - Market Size, Share, Price, Trend and Forecast(DOGAN)

{{Taxonbar, from=Q22662068, from2=Q131911

oryzae
Rice wine
Molds used in food production
Fungi of Japan
Japanese cuisine