New Horizons in Acetogenic Conversion of One-Carbon Substrates and Biological Hydrogen Storage.

Strictly anaerobic, acetogenic (acetate-forming) bacteria are characterized by a reductive pathway in which two mol of CO2 are reduced to one mol of acetyl coenzyme A (acetyl-CoA) and then further to acetate, ethanol, or butyrate. Therefore, they have come into focus for an alternative, CO2-based bioeconomy. Other one-carbon (C1) substrates, such as formic acid or methanol, are promising feedstocks for an alternative bioeconomy using acetogens as biocatalysts that have been somewhat overlooked. In addition, acetogens, such as Acetobacterium woodii and Thermoanaerobacter kivui, have a unique enzyme system capable of reducing CO2 to formate with H2 as reductant that is superior over any chemical catalyst for CO2-based hydrogen storage. Therefore, acetogens are also promising candidates in the hydrogen economy as potential catalysts for hydrogen storage or production.