Departmental Bulletin Paper <PAPERS and REPORTS>Isolation of extremely acid-resistant acetic acid bacterium and its application to production of high-acid vinegar in mesophilic condition

Tajiri, Shintaro  ,  Matsumoto, Katsuki  ,  Kuratomi, Tomohiro  ,  Tanaka, Kenji  ,  Iwai, Hideo  ,  Ueno, Hiro  ,  Hoshino, Munehiro

[概要]福岡県内のお酢メーカーで受け継がれてきた高酸度酢醸造用種酢から酸に対して高度に耐性な酢酸菌を分離した. 16SrRNA遺伝子の相同性その他の形質より本菌をグルコンアセトバクター属細菌と推定し, Gluconacetobacter sp. Munehiroと命名した. 高酸度酢の生産効率化を目的として, 発酵中に基質エタノールを連続的に供給補充する流加培養法において, 発酵槽内のエタノール濃度が酢酸生産速度と酢酸生産量に及ぼす影響を調べた. その結果をもとに, 発酵槽内のエタノール濃度が40 g·L-1から20 g·L-1, 10 g·L-1へと段階的に下がるようエタノール供給を調整することによって, 酢酸の阻害作用を受けやすい中温域(29℃)で発酵槽を冷却することなく205 g·L-1という従来に無い高酢酸濃度のお酢生産に成功した. [Abstract]A new acid-resistant acetic acid bacterium was isolated from the seed vinegar which has been used for the production of highacid vinegar. The bacterium was gram-negative, rod-shaped and motile ; it occurred singly and did not over-oxidize acetic acid. Cellulose formation was not detected. We named the bacterium Gluconacetobacter sp. Munehiro because the sequence of the 16S rRNA gene had 99.9% similarity to that of G. europaeus. The strain is extremely resistant to acetic acid and produces high-concentration acetic acid under mesophilic culture condition. The effects of maintaining the ethanol concentration at different levels on the production of high-acid vinegar were investigated. The acetic acid concentration reached 205 g·L-1 by the stepwise lowering of the ethanol concentration from 40 g·L-1, 20 g·L-1 to 10 g·L-1 at 29℃ without cooling the fermenter. However, the cell concentration, the specific growth rate and the acetic acid production rate were very low because the cell culture suffered by long-time oxygen limitation.

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