Bug enzyme can generate hydrogen from water

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London, Jan 14 (ANI): Using a light-powered bacterial enzyme that releases hydrogen from water, scientists could develop strategies for generating the energy-rich gas.

The lack of low-cost ways to create hydrogen gas is one of the main barriers to the dream of economies fuelled by hydrogen not oil.

A class of enzymes called hydrogenases are used by organisms to convert hydrogen ions to hydrogen gas during anaerobic - without oxygen - respiration.

These enzymes have long interested chemists searching for alternatives to existing, expensive, platinum-catalysed hydrogen generation.

The metal-containing enzymes are all crippled in varying degrees by the presence of oxygen and are also damaged by the very hydrogen they produce.

"That makes them difficult and expensive to use on industrial scales," said chemist Erwin Reisner, at Oxford University in the UK.

Now, according to a report in New Scientist, Reisner and colleague Fraser Armstrong have shown that a newly discovered bacterial hydrogenase is much more resistant to both gases.

The nickel, iron and selenium-rich enzyme, first isolated by Juan Fontecilla-Camps at the University of Joseph Fourier in Grenoble, France, is produced by a sulphate-reducing bacterium.

Its efficiency is unaffected by the presence of hydrogen gas, and it continues to work even if the surrounding air contains 1 percent oxygen by volume - ordinarily even a few parts per million of oxygen would block hydrogenase activity.

The new enzyme also binds strongly to titanium dioxide nanoparticles, making it easy to produce a kind of light-powered, hydrogen-generating dust.

The dust particles are each attached both to the enzyme and to light-absorbing dye molecules that are used in some solar cells.

In the presence of an electron-donating buffer solution, the dye absorbs light and releases excited electrons, which then pass to the enzyme.

Suitably energised, the hydrogenase then converts hydrogen ions from water molecules into hydrogen gas - just as they would during the bacteria's respiration.

After a small sample of the nanoparticles spent 8 hours in a buffer solution under a tungsten-halogen lamp, the headspace gas above the solution was 4.6 percent hydrogen by volume - a result Armstrong calls "promising for a first trial". (ANI)

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