Many bacteria utilize sulfate as an electron acceptor to respire anaerobically to obtain energy by oxidizing organic compounds or molecular hydrogen while reducing sulfate to hydrogen sulfide (46); this process has been described for the gut of the termite Mastotermes darwiniensis (47).
Pyrite formation can produce molecular hydrogen and reduce nitrate to NH3, and HCCH to H2CCH2 (Maden 1995).
Neither butyrate nor butanol were detected in cultures of C. acetobutylicum hbd::int 69), and the formation of molecular hydrogen was significantly reduced.
It has been reported that molecular hydrogen (H2) selectively reduces the hydroxyl radical, the most cytotoxic of the reactive oxygen species (ROS), and can thereby effectively protect cells.
This process releases hydrogen as a waste product, but high levels of hydrogen reduce energy production.
A soluble, electron bifurcating, ferredoxin- and NAD+- reducing hydrogenase oxidizes molecular hydrogen and generates a reduced electron carrier with a very low redox potential, ferredoxin (E' ≈ −500 mV; a redox potential in this range has to be assumed since a ferredoxin is the electron donor for the CO2/CO couple E' = −520 mV).
Under anaerobic conditions, iron and steel alloys are slowly oxidized by the protons of water concomitantly reduced in molecular hydrogen.
Herein, we report the first continuous-flow hydrogenation of p-nitrophenol to p-aminophenol with molecular hydrogen and heterogeneous nano-Cu2O as reducing agent and catalyst, respectively.
Hydrogenases are the key enzymes of biological H2 metabolism catalyzing either H2 oxidation for forming reducing equivalents and protons or reducing protons for producing molecular hydrogen [46, 51]: {text{Hydrogenase reaction:}}{text{ 2H}}^ + {text{ 2e}}^ to {text{ H}}_{ 2} (2}.
Alternatively, Cm2O3 can be obtained by reducing CmO2 with molecular hydrogen: : \mathrm{2\ CmO_2 \+\ H_2\ \longrightarrow \ Cm_2O_3\ +\ H_2O} Furthermore, a number of ternary oxides of the type M II CmO3 are known, where M stands for a divalent metal, such as barium.
