Algae could generate hydrogen for fuel cells

first_imgAn image of Chlamydomonas used in the study. Credit: Surzycki, et al. © 2007 PNAS. Now, a team of biologists including Raymond Surzycki and Jean-David Rochaix from the University of Geneva, and Laurent Cournac and Gilles Peltier, both from the Atomic Energy Commission, the National Center for Scientific Research, and the Mediterranean University, have demonstrated a new method for hydrogen production by algae. In a recent issue of PNAS, the team presented a method using copper to block oxygen generation in the cells of Chlamydomonas reinhardtii that could lead to a consistent cycle of hydrogen production.In order to induce hydrogen production in the algae, cells must be placed in an environment without oxygen but with access to light. To completely deplete the algae’s oxygen supply, the researchers turned off part of a chloroplast gene required for oxygen evolution by adding copper to the cells in an enclosed chamber. Specifically, the addition of copper turned off the Cyc6 promoter, which drives the Nac2 gene, which is required for photosystem II (PSII) synthesis. PSII generates oxygen.Within about three hours, nearly all the oxygen was consumed by respiration, and the algae reached an anaerobic state. Without oxygen, the algae began to synthesize hydrogenase and then produce hydrogen.“Hydrogenase is an enzyme that produces hydrogen by combining electrons derived from the photosynthetic electron transport chain with protons,” Rochaix explained to “It is only produced under anaerobic conditions because the photosynthetically produced oxygen is highly toxic to the hydrogenases.”One of the most significant differences between this method and earlier methods is using copper addition rather than sulfur depletion to repress photosynthetic activity. In past experiments, when the cells’ sulfur was depleted, the cells stopped growing and died after a few days. However, when adding copper, the biologists observed that the cells remained healthy. The rate of hydrogen production in the plants with copper was slightly lower than that of sulfur-depleted plants, but comparable.The scientists also observed that, in healthy cells, the Cyc6 promoter doesn’t stay repressed for long due to “anaerobiosis”—the ability of the cells to survive (and repair) with lack of oxygen. Subsequently, PSII activity is restored, and the cell returns to producing oxygen. What happens when you explode a chemical bond? Citation: Algae could generate hydrogen for fuel cells (2007, November 13) retrieved 18 August 2019 from Explore furtherlast_img

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