Hydrogen-making algae's 'Achilles' heel' discovered

September 29, 2009
Hydrogen-making algae's 'Achilles' heel' discovered
The hydrogen-producing green algae Chlamydomonas reinhardtii

(PhysOrg.com) -- Scientists have discovered how oxygen stops green algae from producing hydrogen. The findings could help those working towards 'solar H2-farms' in which microorganisms produce hydrogen fuel from sunlight and water.

An international team of scientists from Oxford University and universities in Germany report their results in two papers, one in the journal JACS and one in PNAS, published this week.

For years scientists have been interested in how we could, potentially, produce from just sunlight and water to power vehicles and other devices. One option is to use photosynthetic microorganisms that are able to produce hydrogen as well as starch. Green algae are one of the microorganisms that many have suggested could be turned into living hydrogen factories.

‘The hydrogen-producing enzyme found in green algae, known as an iron-iron hydrogenase, has evolved a structure that makes it particularly susceptible to attacking oxygen molecules,’ said Professor Fraser Armstrong from Oxford University’s Department of Chemistry, an author of both papers. ‘Because oxygen is a major by-product of the hydrogen-making photosynthetic process in such organisms, the build-up of oxygen, which rapidly attacks the active site of the enzyme, quickly brings the hydrogen-making process to an irreversible halt. Our work has revealed the mechanism of this process.’

The team used electrochemical kinetic methods to determine the order of events in which oxygen attacks the active site of an iron-iron hydrogenase found in the green algae Chlamydomonas reinhardtii. They combined their observations with data obtained from X-ray . By measuring ripples in the photoelectron of the enzyme under X-ray bombardment they were able to deduce the nature of the damage caused to the active site following attack by oxygen.

Yet while the research reported in PNAS shows just how destructive oxygen is to the enzyme powering ’s hydrogen-making process, the team’s research reported in JACS shows that similar hydrogenases produced by other microorganisms may possess greater tolerance to oxygen, sufficient perhaps to survive in the presence of oxygen released during photosynthetic hydrogen production.

Professor Armstrong said: ‘It shows that whilst we may have found a major obstacle along one route to the biological production of hydrogen, this knowledge could help us to identify new routes where nature could suggest an answer to the problem of ’s destructive effect on hydrogen-producing enzymes.’

The team will shortly be publishing the results of similar research into nickel-iron hydrogenases, enzymes related to those that enable blue-green algae to produce hydrogen.

Provided by Oxford University (news : web)

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1 / 5 (1) Sep 29, 2009
If this could become a less expensive method of producing hydrogen it's great even if hydrogen is not the eventual energy carrier of the future. Making any chemical cheaper will always have spinoff benefits. Biotic generation seems a rather inefficient means of production but maybe lower capital costs and byproducts could make it economical.
not rated yet Sep 30, 2009
Workers in these greenhouses may have to carry oxygen tanks for breathing!
not rated yet Oct 01, 2009
Just what are you going to do with the H2 once you have it? It's not eff to store or use other than making chemicals right away.

Far better is a fast growing biomass like hemp or bamboo and by FT process make about any HC/ syn fuel you want and electricity. Or dry the algae and do the same. Better would be harvesting floating plants, algae from lakes, ponds, rivers and FTing it. This not only makes energy but cleans the water too.

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