Traditional microbial control methods used in sake brewing effectively suppress predominant bacteria emerging during production of rice koji

Rice koji is a raw material used in the production of sake; however, details regarding the microbial flora and their dynamics in rice koji during the production process are poorly understood. Clarifying these issues can contribute to proposing a method and evaluation that will improve the quality of...

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Main Authors: Kota Naganuma, Youji Nakagawa, Susumu Kokubo, Takuya Hashimoto, Kayo Higuchi, Naoko Ariizumi, Masayuki Hayakawa, Hideki Yamamura
Format: Article
Language:English
Published: Taylor & Francis Group 2023-03-01
Series:Biotechnology & Biotechnological Equipment
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Online Access:https://www.tandfonline.com/doi/10.1080/13102818.2023.2271566
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author Kota Naganuma
Youji Nakagawa
Susumu Kokubo
Takuya Hashimoto
Kayo Higuchi
Naoko Ariizumi
Masayuki Hayakawa
Hideki Yamamura
author_facet Kota Naganuma
Youji Nakagawa
Susumu Kokubo
Takuya Hashimoto
Kayo Higuchi
Naoko Ariizumi
Masayuki Hayakawa
Hideki Yamamura
author_sort Kota Naganuma
collection DOAJ
description Rice koji is a raw material used in the production of sake; however, details regarding the microbial flora and their dynamics in rice koji during the production process are poorly understood. Clarifying these issues can contribute to proposing a method and evaluation that will improve the quality of rice koji and sake. The aim of this study was to determine the microflora in rice koji and the effectiveness of the traditional microbial control techniques used in the sake production process. We analyzed the diversity and changes in bacterial flora during rice koji production by amplicon sequencing of the 16S rRNA gene. The predominant taxon in all rice koji samples was family Staphylococcaceae. The microbial population and the changes in its distribution for five consecutive stages in rice koji production were examined by direct colony counting. Bacteria counts in all samples were below the limit of detection initially, then increased rapidly toward the final stage. The predominant bacterial colonies from all samples were yellow and were identified as Staphylococcus gallinarum through 16S rRNA gene sequence similarity. The S. gallinarum isolates exhibited faster growth in pregelatinized rice medium. Interestingly, the growth of S. gallinarum isolates was suppressed by low temperature (12 °C), ethanol concentration (≥6%) and the addition of lactic acid, which are traditional microbial control methods used during sake fermentation. Therefore, proper control of the traditional sake production process can effectively inhibit the growth of undesirable bacteria such as S. gallinarum that emerge during the production of rice koji.
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publishDate 2023-03-01
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spelling doaj-art-b6359ea388524824aabeab0c13172bdf2025-08-20T02:49:29ZengTaylor & Francis GroupBiotechnology & Biotechnological Equipment1310-28181314-35302023-03-0137110.1080/13102818.2023.2271566Traditional microbial control methods used in sake brewing effectively suppress predominant bacteria emerging during production of rice kojiKota Naganuma0Youji Nakagawa1Susumu Kokubo2Takuya Hashimoto3Kayo Higuchi4Naoko Ariizumi5Masayuki Hayakawa6Hideki Yamamura7Graduate Faculty of Interdisciplinary Research, University of Yamanashi, Kofu, Yamanashi, JapanGraduate Faculty of Interdisciplinary Research, University of Yamanashi, Kofu, Yamanashi, JapanGraduate Faculty of Interdisciplinary Research, University of Yamanashi, Kofu, Yamanashi, JapanFood & Liquor and Biotechnology Section, Yamanashi Industrial Technology Center, Kofu, Yamanashi, JapanFood & Liquor and Biotechnology Section, Yamanashi Industrial Technology Center, Kofu, Yamanashi, JapanFood & Liquor and Biotechnology Section, Yamanashi Industrial Technology Center, Kofu, Yamanashi, JapanYamanashi Prefectural University, Kofu, Yamanashi, JapanGraduate Faculty of Interdisciplinary Research, University of Yamanashi, Kofu, Yamanashi, JapanRice koji is a raw material used in the production of sake; however, details regarding the microbial flora and their dynamics in rice koji during the production process are poorly understood. Clarifying these issues can contribute to proposing a method and evaluation that will improve the quality of rice koji and sake. The aim of this study was to determine the microflora in rice koji and the effectiveness of the traditional microbial control techniques used in the sake production process. We analyzed the diversity and changes in bacterial flora during rice koji production by amplicon sequencing of the 16S rRNA gene. The predominant taxon in all rice koji samples was family Staphylococcaceae. The microbial population and the changes in its distribution for five consecutive stages in rice koji production were examined by direct colony counting. Bacteria counts in all samples were below the limit of detection initially, then increased rapidly toward the final stage. The predominant bacterial colonies from all samples were yellow and were identified as Staphylococcus gallinarum through 16S rRNA gene sequence similarity. The S. gallinarum isolates exhibited faster growth in pregelatinized rice medium. Interestingly, the growth of S. gallinarum isolates was suppressed by low temperature (12 °C), ethanol concentration (≥6%) and the addition of lactic acid, which are traditional microbial control methods used during sake fermentation. Therefore, proper control of the traditional sake production process can effectively inhibit the growth of undesirable bacteria such as S. gallinarum that emerge during the production of rice koji.https://www.tandfonline.com/doi/10.1080/13102818.2023.2271566Rice kojiS. gallinarumbacterial floramicrobial control
spellingShingle Kota Naganuma
Youji Nakagawa
Susumu Kokubo
Takuya Hashimoto
Kayo Higuchi
Naoko Ariizumi
Masayuki Hayakawa
Hideki Yamamura
Traditional microbial control methods used in sake brewing effectively suppress predominant bacteria emerging during production of rice koji
Biotechnology & Biotechnological Equipment
Rice koji
S. gallinarum
bacterial flora
microbial control
title Traditional microbial control methods used in sake brewing effectively suppress predominant bacteria emerging during production of rice koji
title_full Traditional microbial control methods used in sake brewing effectively suppress predominant bacteria emerging during production of rice koji
title_fullStr Traditional microbial control methods used in sake brewing effectively suppress predominant bacteria emerging during production of rice koji
title_full_unstemmed Traditional microbial control methods used in sake brewing effectively suppress predominant bacteria emerging during production of rice koji
title_short Traditional microbial control methods used in sake brewing effectively suppress predominant bacteria emerging during production of rice koji
title_sort traditional microbial control methods used in sake brewing effectively suppress predominant bacteria emerging during production of rice koji
topic Rice koji
S. gallinarum
bacterial flora
microbial control
url https://www.tandfonline.com/doi/10.1080/13102818.2023.2271566
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