any kinds of algae and cyanobacteria are capable of using energy from sunlight to split water molecules and release hydrogen. One reason this approach hasn’t yet been harnessed for fuel production is that under ordinary circumstances, hydrogen production takes a back seat to the production of compounds that the organisms use to support their own growth.
But Shuguang Zhang, associate director of MIT’s Center for Biomedical Engineering, and postdocs Iftach Yacoby and Sergii Pochekailov, together with colleagues at Tel Aviv University in Israel and the National Renewable Energy Laboratory in Colorado, have found a way to use bioengineered proteins to flip this preference, allowing more hydrogen to be produced.
“The algae are really not interested in producing hydrogen, they want to produce sugar,” Yacoby says. “The sugar is what they need for their own survival, and the hydrogen is just a byproduct. But a multitasking enzyme, introduced into the liquid where the algae are at work, both suppresses the sugar production and redirects the organisms’ energies into hydrogen production. The work is described in a paper published in the Proceedings of the National Academy of Sciences, and was supported in part by a European Molecular Biology Organization postdoctoral fellowship, the Yang Trust Fund and the U.S. Department of Energy’s National Renewable Energy Laboratory.
Adding the bioengineered enzyme increases the rate of algal hydrogen production by about 400 percent, Yacoby says. The sugar production is suppressed but not eliminated, he explains, because “if it went to zero, it would kill the organism.”
The research demonstrates for the first time how the two processes carried out by algae compete with each other; it also shows how that competition could be modified to favor hydrogen production in a laboratory environment. Zhang and Yacoby plan to continue developing the system to increase its efficiency of hydrogen production.
Ultimately, such a system could be used to produce hydrogen on a large scale using water and sunlight. The hydrogen could be used directly to generate electricity in a fuel cell or to power a vehicle, or could be combined with carbon dioxide to make methane or other fuels in a renewable, carbon-neutral way, the researchers say.