KIMOTO SHUBO is a traditional seed mash producing method in sake brewing. Yeast is cultivated vigorously in open systems without contamination by bacteria or wild yeast. In the process, contaminated microorganisms are inhibited from growing by a nitrite/nitrate system in the mother water and lactic acid produced by lactic acid bacteria. Finally, under the low pH condition, the sake yeast is grown predominantly in the mash. However, in the brewer' s house, there is a phenomenon in which the

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... te is not eliminated in the mash. This factor was researched using model mash by sake koji obtained from sake brewer' s houses. The microorganisms in the koji eliminated the nitrite in mash. Y-11393 strain was identified as Pichia angusta. The strain oxidized nitrite to eliminate it from the mash. It is believed that the yeast assimilated nitrate, which is a low toxic substance for yeast. The strain had tolerance against nitrite and could grow under 1-5mM nitrite conditions. It also eliminated nitrite up to 6-16% for 4 days. Moreover, the strain had acid tolerance and ethanol tolerance up to 5% ethanol and 1.1% lactic acid. The yeast eliminated nitrite in the model moto-mash. Also, the yeast cells between the mid-log phase and late-log phase thoroughly eliminated nitrite. It is obvious that the yeast has the ability to remove nitrite in the KIMOTO method. Key words: 生酛酒母,亜硝酸,麹,Pichia angusta ────────────────────────── 諸言 清酒醸造における生酛酒母や山廃酒母は,伝統的な 微生物遷移を利用して,開放下で酵母を純粋培養する 方法である。その操作の特徴として繁雑で,期間が 1 カ月と長いことが挙げられる。 これらの生酛酒母や山廃酒母は初期に 10℃以下と 極低温下で,水や空気中に由来する硝酸還元菌,おも に Psudomonas 属が仕込み水中に含まれる硝酸を亜 硝酸へと変換する。芹沢 1-5) はこの亜硝酸と乳酸との 相乗効果により,おもに麹に由来する野生酵母の生育 を阻害していると報告している。しかし,原ら 6) は生 酛酒母に存在する亜硝酸濃度は 15ppm 程度で野生酵 母の生育阻害は及ぼさず,その生育阻害は高糖濃度や * コレスポンディングオーサー