"Bodai-moto" is the "moto" (yeast mash), with which "Nanto moro-haku" (several kinds of "soboshu" [monk's sake] having the highest quality), especially the name-brand sake "Bodaisen," was made through fermentation at Shoryaku-ji Temple on Mt. Bodai in Nara.
The term also refers to the sake brewing method which uses this moto.
Bodai-moto was mentioned in some books, such as "Goshu-no-nikki," the oldest book on sake brewing techniques written in the early Muromachi period, and "Domoshuzoki," the best and the most detailed book on sake brewing techniques written in the early Edo period, and the descriptions show us how advanced the sake brewing techniques in those days were.
Bodai-moto was also called "ikaki-moto," because it used "ikaki" (a bamboo sieve), which is like the bamboo (or plastic) colander today.
The preparation of materials for brewing new sake begins when the lingering summer heat is still severe. The steamed rice is put into ikaki, and is converted into moto by the lactic acid fermentation in water. The fermentation smells bad but proceeds quickly thanks to the high temperature, so it is said that moto can be made without issue even during summer.
The steamed rice is fermented strongly. "Soe" (the production process of "moromi" [the main mash]) is usually repeated three times, but in the case of Bodai-moto, it is repeated twice.
As "koji" (Aspergillus oryzae) is cultivated, the rice begins to taste sweet at first because of the saccharification of the starch, before developing a bitter and spicy taste, and this is when soe should be started. The amount of "koji-mai" (the rice in which the mold of "koji" [Aspergillus oryzae] is cultivated) is 60% of the steamed rice for both moto and moromi.