Crumb Trail
     an impermanent travelogue
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Thursday, February 23, 2006

It's a dead common trope in SF to have biofactories that produce all sorts of wonders, but it is still an infant science despite being quite ancient. Beer, woad, and a variety of cultured foods have been around for along time. Progress seems to be accelerating.

The new strain of algae, known as C. reinhardtii, has truncated chlorophyll antennae within the chloroplasts of the cells, which serves to increase the organism's energy efficiency. In addition, it makes the algae a lighter shade of green, which in turn allows more sunlight deeper into an algal culture and therefore allows more cells to photosynthesize.

"An increase in solar conversion efficiency to 10 percent ... is thought to be enough to make the mass culture of algae viable," . . .

Currently, the algae cells cycle between photosynthesis and hydrogen production because the hydrogenase enzyme which makes the hydrogen can’t function in the presence of oxygen. Researchers hope to further boost hydrogen production by using genetic engineering to close up pores that oxygen seeps through.

Melis got involved in this research when he and Michael Seibert, a scientist at the National Renewable Energy Laboratory in Golden, Colorado, figured out how to get hydrogen out of green algae by restricting sulfur from their diet. The plant cells flicked a long-dormant genetic switch to produce hydrogen instead of carbon dioxide. But the quantities of hydrogen they produced were nowhere near enough to scale up the process commercially and profitably.

"When we discovered the sulfur switch, we increased hydrogen production by a factor of 100,000," says Seibert. "But to make it a commercial technology, we still had to increase the efficiency of the process by another factor of 100."

Melis’ truncated antennae mutants are a big step in that direction. Now Seibert and others (including James Lee at Oak Ridge National Laboratories and J. Craig Venter at the Venter Institute in Rockville, Maryland) are trying to adjust the hydrogen-producing pathway so that it can produce hydrogen 100 percent of the time.

This is important I think since the key limitation of biofuels at present is that they are based on a 1% efficient process, which is about the median for plants. 99% of the solar energy that falls on them isn't used. But 10% efficiency rivals a low end solar cell.

posted by back40 | 2/23/2006 11:56:00 PM


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