海洋深層水（DOW）から分離した出芽酵母 Saccharomyces cerevisiae SCAK-1株（分離株）の産業利用に向けて，出芽酵母の利用時に曝される各種ストレスに対する代謝機能の応答性を検討した．本研究では，解糖系による培養液重量の減少量を出芽酵母の代謝機能と考えた．環境ストレスとして温度，浸透圧，アルコールおよび酸化の4種類のストレスを選んだ．基準株の代謝は，高温ストレス，酸化ストレス，高濃度のアルコールストレスの負荷で著しく低下したが，分離株の代謝はこれらのストレス負荷では低下しなかった。なお，浸透圧ストレスはどちらの株の代謝にも影響を与えなかった．またDOW環境において分離株が喪失していたマルトース資化性は，グルコース制御の解除により復元された．本研究により分離株は，高いストレス耐性を有し，マルトース資化性という出芽酵母にとっての重要な能力も復元されたことから，今後幅広い産業分野での利用発展が期待される．

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Deep seawater (DSW) contains various resources useful for human life, including cold energy. In this research, we focused on lactic acid bacteria, which are expected to prevent diabetes, hypertension, and obesity. Thirty-two strains of lactic acid bacteria were isolated from Izu-Akazawa DSW. For comparison, 34 strains from surface seawater (SSW) or seaweed from other sources and 25 strains from commercial fermented food (FF) were prepared. All isolates from the three isolation sources (DSW, SSW, FF) were tested for cell growth potential by culture conditions and showed little difference in general characteristics. Next, considering the use of the isolate, the ability of the isolate to ferment soymilk was studied. As a result, there was a difference in the fermentability of soymilk among the isolates from each source. To study the function of soymilk fermented by the isolates, their inhibitory effect against α-glucosidase activity was evaluated. α-Glucosidase activity was well known as a key effector of diabetes, a national disease in Japan today. As a result, there were differences in the inhibitory effect on α-glucosidase activity of soymilk fermented by the isolates. The inhibitory effect of soymilk fermented by isolates from DSW on α-glucosidase activity was shown to be 5.0±0.7 units/mL, which was the strongest among the isolates from three kinds of sources (p＜0.05, SSW; 4.2±1.7 units/mL, FF; 3.3±1.5 units/mL). Then, we performed 16S rDNA analysis of each isolate and identified it as a Lactobacillus species level. As a result, the lactic acid bacteria species isolated from each source had a characteristic, which was the difference in the content of Lactiplantibacillus plantarum. The content of L. plantarum in isolates was independent of soymilk fermentability but associated with inhibitory effect on α-glucosidase activity of fermented soymilk. This study suggested that DSW is a useful source for the isolation of certain lactic acid bacteria, especially L. plantarum. In the future, it is expected that the use of L. plantarum isolated from DSW will expand to the field of human health.

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