Association Yeast No. 2 - 協会二号酵母
From Fushimi to forgotten: how wartime sake policy quietly erased one of Japan's brewing yeasts
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Discontinued yeast with limited usage
Lineage
Prefecture: Kyoto 京都府
Developer: Isolated at Gekkeikan Brewery 月桂冠 in Fushimi.
Year: Isolated 1912 Meiji Period (1868-1912)
History
Isolated in the late Meiji Period (1868-1912) at Gekkeikan Brewery 月桂冠 in Fushimi, Kyoto. Some references note it was isolated from a tank of new sake (shinshu). It was distributed by the Brewing Society of Japan 公益財団法人日本醸造協会 from 1917 to 1939.
Distribution ceased abruptly at the outset of the Second World War. Several factors contributed to its discontinuation: the post-war situation, the industry’s shift toward stronger yeasts capable of producing higher alcohol, and the rapid economic expansion that followed. Adding to this, the authorised production of Sanzo-shu 三増酒, a wartime and post-war measure that artificially tripled sake output by diluting the base sake with added alcohol, sugars, and other additives which fundamentally reshaped industry priorities. As Sanzo-shu came to dominate the market, the demand for the kind of high-quality sake that No. 2 excelled at all but disappeared. The style’s long reign, lasting until its prohibition in 2006, left a lasting reputational mark and pushed brewers toward higher-yield, higher-alcohol yeasts. Though it is worth noting that No. 2 was generally well regarded for its aroma and flavour at the time of its use.
A 1925 issue of the Journal of the Brewing Society of Japan described it as:
Quote
“However, this yeast produces a strong aroma during fermentation, emitting a fragrance reminiscent of apples, and yields excellent sake. Furthermore, it produces abundant foam, and once it begins to bubble, its fermentation is more vigorous than that of Yeast No. 1. Apart from the above, this yeast produces extremely small amounts of acid and amino acids.”
鎌治郎江田. ‘酒質改善上優良酵母菌の利用’. 日本釀造協會雜誌, vol. 20, no. 11, 1925, pp. 2–7, https://doi.org/10.6013/jbrewsocjapan1915.20.11_2.
As it fell out of favour, No. 2 was succeeded by Association Yeast No. 6 - 協会六号酵母, Association Yeast No. 7 - 協会七号酵母, and Association Yeast No. 9 - 協会九号酵母. It is no longer in commercial use, though it has seen a handful of notable revivals: Gekkeikan Brewery 月桂冠 released a limited run on the yeast’s 100th anniversary, and Obuse Winery (Sogga père et fils) of Nagano 長野県 has used it. Both solo and blended with No. 6 in its select Le Saké Érotique releases.
Note
Given that No. 2 is preserved by both the Brewing Society of Japan 公益財団法人日本醸造協会 and the National Research Institute of Brewing (NRIB), and given the current market’s growing appetite for less conventional styles, could there be a place for it again?
Characteristics
No. 2 is generally described as a delicate yeast, notable for its rounded cell morphology. It produces a restrained, elegant aroma but is slow to produce a vigorous fermentation initially. Compared to Association Yeast No. 1 - 協会一号酵母, it is more sensitive to elevated temperatures and takes longer to build alcohol. Factors that promoted its replacement once higher-performing strains like No. 6, 7, and 9 became available.
This yeast produces a crisp finish, with a nice aroma and it is suited for lower temperature fermentations (at the time), perhaps due to its sensitivity to heat. It produces a good-tasting sake reported to produce low acid and amino content in some reports while at the same time it is said the such acidity is high when compared to the modern strains.
No. 2 yields sake with a crisp finish and pleasing aromatic character. It is well-suited to low-temperature fermentations (of the time), likely in part due to its heat sensitivity. Reports consistently note low acid and amino acid production, though would like to flag an apparent contradiction in the sources. Some older accounts describe its acidity as low, while certain comparisons with modern strains characterise it as relatively high. This is likely a reflection of the reference point rather than any inconsistency in the yeast itself.
References
正宗＠酒造技能士. “【14】清酒醸造の微生物(1) －酵母①－.” Note（ノート）, 29 June 2023, note.com/masamune_sake/n/n7864aa25b71b.
灘酒研究会. “きょうかい酵母 | 灘の酒用語集.” Nada-Ken.com, www.nada-ken.com/main/jp/index_ki/192.html. Accessed 16 Apr. 2026.
Jizake-ya. “酵母についての研究.” Jizakeya.co.jp, jizakeya.co.jp/labo/20020404112556.html. Accessed 16 Apr. 2026.
大矢禎一. ‘清酒酵母こんじゃく物語’. JOURNAL OF THE BREWING SOCIETY OF JAPAN, vol. 112, no. 4, 2017, pp. 207–207. DOI.org (Crossref), https://doi.org/10.6013/jbrewsocjapan.112.207.
月桂冠株式会社. “蔵元直送・360本限定京都の米・水・技、百年の刻（とき）を味わう 月桂冠「百年酵母仕込み 純米大吟醸」数量限定発売｜ニュース｜月桂冠.” 月桂冠, 2021, www.gekkeikan.co.jp/company/news/detail/247/. Accessed 16 Apr. 2026.
SAKETIMESPR. “100年の時を経て「きょうかい2号」の日本酒が復活！─ 月桂冠の蔵付き酵母で醸す「百年酵母仕込み」が未来をつなぐ | 日本酒専門WEBメディア「SAKETIMES」.” _SAKETIMES | 日本酒をもっと知りたくなるWEBメディア, 20 Oct. 2019, jp.sake-times.com/special/pr/pr_gekkeikan4_004. Accessed 16 Apr. 2026.
鎌治郎江田. ‘酒質改善上優良酵母菌の利用’. 日本釀造協會雜誌, vol. 20, no. 11, 1925, pp. 2–7, https://doi.org/10.6013/jbrewsocjapan1915.20.11_2.
29ONチャンネル. “【日本酒 おすすめ】協会2号酵母を使用した「ソガペールエフィス ル サケ エロティック ヌメロ ドゥー」。世界的に有名なワイナリー「小布施ワイナリー」が造る日本酒とは！？.” YouTube, 9 June 2020, www.youtube.com/watch?v=VynyhXqdhfI. Accessed 16 Apr. 2026.