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Direct and Reversible Hydrogenation of CO2 to Formate by a Bacterial Carbon Dioxide Reductase

Science  13 Dec 2013:
Vol. 342, Issue 6164, pp. 1382-1385
DOI: 10.1126/science.1244758

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Making CO2 Work for You

Converting carbon dioxide (CO2) to formic acid (HCOOH) is an attractive substrate for the storage and recovery of hydrogen (H2) for use as fuel. Because CO2 is relatively stable, however, its hydrogenation typically requires extreme conditions. Schuchmann and Müller (p. 1382: see the Perspective by Pereira) isolated a hydrogen-dependent carbon dioxide reductase from Acetobacterium woodii that is nearly 2000-fold more effective than the fastest known chemical catalysts. The process, which relies on the formation of formate as a chemical intermediate, also works well in whole-cell systems of A. woodii when certain metabolic pathways are inhibited. The enzyme, whether isolated or present in host bacteria, may lead to the design of more efficient fuel cells capable of functioning under less harsh conditions than fuel cells based on chemical reactions alone.

Abstract

Storage and transportation of hydrogen is a major obstacle for its use as a fuel. An increasingly considered alternative for the direct handling of hydrogen is to use carbon dioxide (CO2) as an intermediate storage material. However, CO2 is thermodynamically stable, and developed chemical catalysts often require high temperatures, pressures, and/or additives for high catalytic rates. Here, we present the discovery of a bacterial hydrogen-dependent carbon dioxide reductase from Acetobacterium woodii directly catalyzing the hydrogenation of CO2. We also demonstrate a whole-cell system able to produce formate as the sole end product from dihydrogen (H2) and CO2 as well as syngas. This discovery opens biotechnological alternatives for efficient CO2 hydrogenation either by using the isolated enzyme or by employing whole-cell catalysis.

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