Membrane-anchored HDCR nanowires drive hydrogen-powered CO fixation.

Filamentous enzymes have been found in all domains of life, but the advantage of filamentation is often elusive. Some anaerobic, autotrophic bacteria have an unusual filamentous enzyme for CO fixation-hydrogen-dependent CO reductase (HDCR)-which directly converts H and CO into formic acid. HDCR reduces CO with a higher activity than any other known biological or chemical catalyst, and it has therefore gained considerable interest in two areas of global relevance: hydrogen storage and combating climate change by capturing atmospheric CO.

Formate-driven H production by whole cells of Thermoanaerobacter kivui.

Background: In times of global warming there is an urgent need to replace fossil fuel-based energy vectors by less carbon dioxide (CO)-emitting alternatives. One attractive option is the use of molecular hydrogen (H) since its combustion emits water (HO) and not CO. Therefore, H is regarded as a non-polluting fuel.

Capture of carbon dioxide and hydrogen by engineered Escherichia coli: hydrogen-dependent CO reduction to formate.

In times of global climate change and the fear of dwindling resources, we are facing different considerable challenges such as the replacement of fossil fuel-based energy carriers with the coincident maintenance of the increasing energy supply of our growing world population. Therefore, CO capturing and H storing solutions are urgently needed. In this study, we demonstrate the production of a functional and biotechnological interesting enzyme complex from acetogenic bacteria, the hydrogen-dependent CO reductase (HDCR), in the well-known model organism Escherichia coli.

Revealing formate production from carbon monoxide in wild type and mutants of Rnf- and Ech-containing acetogens, Acetobacterium woodii and Thermoanaerobacter kivui.

Acetogenic bacteria have gained much attraction in recent years as they can produce different biofuels and biochemicals from H plus CO or even CO alone, therefore opening a promising alternative route for the production of biofuels from renewable sources compared to existing sugar-based routes. However, CO metabolism still raises questions concerning the biochemistry and bioenergetics in many acetogens. In this study, we focused on the two acetogenic bacteria Acetobacterium woodii and Thermoanaerobacter kivui which, so far, are the only identified acetogens harbouring a H -dependent CO reductase and furthermore belong to different classes of 'Rnf'- and 'Ech-acetogens'.

Whole-cell biocatalysis for hydrogen storage and syngas conversion to formate using a thermophilic acetogen.

Background: In times of global climate change, the conversion and capturing of inorganic CO have gained increased attention because of its great potential as sustainable feedstock in the production of biofuels and biochemicals. CO is not only the substrate for the production of value-added chemicals in CO-based bioprocesses, it can also be directly hydrated to formic acid, a so-called liquid organic hydrogen carrier (LOHC), by chemical and biological catalysts. Recently, a new group of enzymes were discovered in the two acetogenic bacteria and which catalyze the direct hydrogenation of CO to formic acid with exceptional high rates, the hydrogen-dependent CO reductases (HDCRs).

Hydrogenation of CO at ambient pressure catalyzed by a highly active thermostable biocatalyst.

Background: Replacing fossil fuels as energy carrier requires alternatives that combine sustainable production, high volumetric energy density, easy and fast refueling for mobile applications, and preferably low risk of hazard. Molecular hydrogen (H) has been considered as promising alternative; however, practical application is struggling because of the low volumetric energy density and the explosion hazard when stored in large amounts. One way to overcome these limitations is the transient conversion of H into other chemicals with increased volumetric energy density and lower risk hazard, for example so-called liquid organic hydrogen carriers such as formic acid/formate that is obtained by hydrogenation of CO.