Project focuses on production of hydrogen from bacteria and sunlight

The ASU researchers, who have years of experience working in this field, are using a cyanobacterium with a known genome and have developed it into a model organism for genetic and metabolic engineering studies. Using its natural photosynthesis machinery, “we are now starting to direct more of the photosynthetic activity into biofuel production, yielding organisms that convert substantially more of the harvested energy into biofuels,” Vermaas said.

One of the main challenges for the researchers is finding an enzyme for hydrogen production, called hydrogenase, which can operate in the presence of oxygen. Hydrogenase enzymes are a key component to hydrogen production through the photosynthesis process. However, they currently are very sensitive to oxygen, a natural by-product of the splitting of water (H2O).

“If you make photosynthetic hydrogen, you also make oxygen and you have a problem because oxygen inactivates the very enzyme that you want to have working,” Vermaas explained.

One part of the project, headed up by Ferran Garcia-Pichel in the School of Life Sciences, is to find heartier forms of hydrogenase. Garcia-Pichel will be looking at systems that occur in nature.

“Preliminary data suggest that in a variety of natural habitats cyanobacteria can produce hydrogen, which means that unless there is some way the cells exclude oxygen from the process, their hydrogenase enzyme must be oxygen tolerant,” Vermaas said.

“Boosting the oxygen tolerance of the hydrogenase is really a key to the overall system,” he added. With a robust hydrogenase enzyme, the next step is to incorporate their genes into the model cyanobacterial system. But the way they are incorporated and how the oxygen-tolerant hydrogenase is aligned with other enzymes in the cyanobacteria are critical to getting the system to work efficiently.

“We need to be able to effectively connect the hydrogenase to the photosynthetic reaction center complexes of the cyanobacteria,” Vermaas says. “We can do that through metabolic engineering.”

Each cyanobacterial cell is about 1.5 µm in size, much smaller than what can be seen individually by the human eye. Bacteria’s evolutionary drive is to multiply and in that process electrons and protons are used for the generation of energy and as building blocks for growth of the organism. In the modified cyanobacterial system, Vermaas wants to divert electrons from their normal pathways and push them into new pathways that result in hydrogen production.