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.