Photosynthetic microorganisms are an attractive option to produce renewable H2. Cyanobacteria can perform oxygenic photosynthesis and use sunlight energy to extract reducing equivalents from water. The resulting reducing equivalents could be fed directly to a hydrogenase system yielding H2. However, one major difficulty is that most hydrogen-evolving hydrogenases including those of cyanobacteria are inhibited by the O2 produced from photosynthesis. Certain bacteria are reported to have O2-tolerant hydrogenases, but these microbes do not split water, and require other more expensive feedstocks. To solve these problems, we have been genetically transferring O2-tolerant hydrogenases from other bacteria into cyanobacteria. Ultimately, these hybrid systems will use the photosynthetic machinery of the cyanobacterial hosts to perform the water-oxidation reaction with the input of solar energy, and couple the resulting reducing equivalents to the O2-tolerant bacterial hydrogenase to produce hydrogen. In this talk we discuss recent progress modifying the hydrogenase enzyme for improved hydrogen evolution activity, modifying the regulation of the hydrogenase to increase expression, and improving the hydrogenase interaction with photosynthetic electron donors.

Progress developing a cyanobacterial system for oxygen-tolerant, light-driven hydrogen production from water

247th National Meeting (2014)

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