Scientists discover new possibilities for hydrogen-producing algae

Washington, March 25 (ANI): Researchers studying a hydrogen-producing, single-celled green alga, Chlamydomonas reinhardtii, have unmasked a previously unknown fermentation pathway that may open up possibilities for increasing hydrogen production.

C. reinhartii, a common inhabitant of soils, naturally produces small quantities of hydrogen when deprived of oxygen. Like yeast and other microbes, under anaerobic conditions this alga generates its energy from fermentation.

During fermentation, hydrogen is released though the action of an enzyme called hydrogenase, powered by electrons generated by either the breakdown of organic compounds or the splitting of water by photosynthesis.

Normally, only a small fraction of the electrons go into generating hydrogen.

However, a major research goal has been to develop ways to increase this fraction, which would raise the potential yield of hydrogen.

In the new study, researchers at the Carnegie Institution's Department of Plant Biology, the National Renewable Energy Laboratory (NREL), and the Colorado School of Mines (CSM), examined metabolic processes in a mutant strain that was unable to assemble an active hydrogenase enzyme.

The researchers expected the cell's metabolism to compensate by increasing metabolite flow along other known fermentation pathways, such as those producing formate and ethanol as end products.

Instead, the algae activated a pathway leading to the production of succinate, which was previously not associated with fermentation metabolism in C. reinhardtii.

Notably, succinate, a widely used industrial chemical normally synthesized from petroleum, is included in the Department of Energy's list of the top 12 value added chemicals from biomass.

"We actually didn't know that this particular pathway for fermentation metabolism existed in the alga until we generated the mutant," said Carnegie's Arthur Grossman.

"This finding suggests that there is significant flexibility in the ways that soil-dwelling green algae can metabolize carbon under anaerobic conditions," he added.

"By blocking and modifying some of these metabolic pathways, we may be able to augment the donation of electrons to hydrogenase under anaerobic conditions and produce elevated levels of hydrogen," he further added.

Grossman led the effort to generate a fully sequenced Chlamydomonas genome, which has allowed researchers to identify key genes encoding proteins involved in both fermentation and hydrogen production.

Grossman feels that it is of immediate importance to generate new mutant strains to help us understand how we may be able to alter fermentation metabolism and the production of hydrogen. (ANI)