報告書番号

V10033

タイトル（和文）

電気を用いた未利用バイオマスからの物質生産（その１）－グリセロール変換微生物の探索と電気化学的活性制御－

タイトル（英文）

Production of useful materials from waste biomass by electrolysis (Part I) -Electrochemical screening and activity control of microbial conversion of glycerol-

概要 （図表や脚注は「報告書全文」に掲載しております）

微生物の中には特殊な物質変換機能を有するものが含まれる一方、従来の培養手法では獲得が困難な微生物が多い。当所で開発した電気培養法は、微生物の生育および代謝を電気化学的に制御することで、従来法で培養困難な微生物の培養にも成功している。そこで電気培養を利用して新たな物質生産系の提案につなげることを目的とし、バイオディーゼル生成過程で排出されるグリセロールの微生物変換に着目し、電気培養による微生物の探索と、微生物変換活性の電位依存性を調査した。環境微生物群に対し、グリセロール共存下の電気培養を実施した結果、顕著な微生物の増殖が生じ、グリセロールからエタノールへの変換が見られた。遺伝子解析の結果、増殖した微生物はPaenibacillus属でった。エタノール生成は、-0.2V以下の還元電位でのみ生じたことから、エタノール代謝に含まれる還元反応に、電子が供給され促進されたものと推測された。

概要 （英文）

The development of efficient microbial processes to produce useful products from waste biomass is a promising route that is expected to contribute to the construction of a low-carbon society. Although environmental bacteria might have special functions such as material conversion, their cultivation techniques have not been fully established. Therefore, screening of bacteria with new functions is usually difficult. The electrochemical cultivation method developed at our institute allows the acquisition of previously uncultured bacteria from the environment by controlling the redox potential during cultivation. Therefore, bacteria for producing useful materials from waste biomass are expected to be obtained through electrochemical cultivation. In this report, we describe our search for a bacterium that can generate ethanol from glycerol, which is a byproduct of biodiesel production from oil plants, by means of the electrochemical cultivation technique. Electrochemical cultivation of environmental bacteria was performed under a potential of -0.6 V vs. Ag/AgCl with 1 g/L of glycerol. After 3 weeks of cultivation, the glycerol in the medium was undetectable and significant amount of ethanol was observed. Three kinds of bacteria were found in the medium after the cultivation; they were identified as belonging to the group Paenibacillus by genomic analysis. In experiments with electrochemical cultivation at various potentials, ethanol generation was observed at a potential less than -0.2 V. Since the metabolic pathway for glycerol-to-ethanol conversion inside of bacteria includes several reduction steps, we conclude that ethanol production might be accelerated by the reducing conditions created during electrochemical cultivation.

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