[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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In the current study, the usability of weed and bean curd refuse pretreated with 30V of a direct electric current was investigated for acetic acid fermentation and hydrogen production, respectively. The solubilization and the elution of soluble substances such as polysaccharides were enhanced by pretreatment. Moreover, the contaminants attached to the surface of the raw materials were sterilized by pretreatment. Acetic acid fermentation from pretreated weed performed satisfactory and the culture broth exhibited an antibacterial activity against bacteria. Also, the amount of hydrogen produced from the pretreated bean curd refuse totaled twice as much as that from untreated bean curd refuse.

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We studied the relation between sake yeast and lactic acid bacteria (acid forming bacteria) with a focus on the influence on the formation of excessive acid in the main mash of sake brewing. Our experiments confirmed the following results: The fermentation progress varies if growth rate (doubling time) of the yeast differs even though the ratio of yeast’s living cells (CFU/total cells) may be more than 80% and their fermentability (nanogram carbon dioxide generated by alcohol fermentation with one yeast cell for one hour: ng/hr/cell) hardly shows any difference. The reason for this was that their growth rates, namely, the time when yeasts reached the maximum cell number (ca. 2x10⁸/ml) differed.
Though the invasion of lactic acid bacteria can not be avoided in sake main mash as the mash is fermented in an open vessel without special sterilization, the growth and activities of lactic acid bacteria are suppressed because the necessary doubling time of the sake yeast is shorter than that of the bacteria under the conditions in the main mash. However, the use of yeast with a growth rate lower than 60% of the usual one enhanced the competitive growth of the lactic acid bacteria; as a result, the period for the main mash was prolonged, and its acidity increased abnormally.
When using yeast with a decreased growth rate, two days of odori should be taken to multiply the number of yeast cells (ca. 2x10⁸/ml) sufficiently in a three-step mashing of sake brewing.

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