Progress toward a biomimetic leaf: 4,000 h of hydrogen production by coating-stabilized nongrowing photosynthetic Rhodopseudomonas palustris

Authors

  • Jimmy L. Gosse,

    1. BioTechnology Institute, University of Minnesota, 140 Gortner Laboratory, St. Paul, MN 55108
    2. Dept. of Biochemistry, Molecular Biology, Biophysics, University of Minnesota, St. Paul, MN 55108
    Current affiliation:
    1. Dept. of Biological and Agricultural Engineering, 3100 Faucette Drive, North Carolina State University, Raleigh, NC 27695-7625
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  • Brian J. Engel,

    1. Dept. of Biochemistry, Molecular Biology, Biophysics, University of Minnesota, St. Paul, MN 55108
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  • Jeremy C.-H. Hui,

    1. Dept. of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455
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  • Caroline S. Harwood,

    1. Dept. of Microbiology, University of Washington, Seattle, WA 98195
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  • Michael C. Flickinger

    Corresponding author
    1. BioTechnology Institute, University of Minnesota, 140 Gortner Laboratory, St. Paul, MN 55108
    2. Dept. of Biochemistry, Molecular Biology, Biophysics, University of Minnesota, St. Paul, MN 55108
    • Dept. of Microbiology, Chemical and Biomolecular Engineering, Golden LEAF Biomanufacturing Training and Education Center, North Carolina State University, Campus Box 7928, Raleigh, NC 27695
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Abstract

Intact cells are the most stable form of nature's photosynthetic machinery. Coating-immobilized microbes have the potential to revolutionize the design of photoabsorbers for conversion of sunlight into fuels. Multi-layer adhesive polymer coatings could spatially combine photoreactive bacteria and algae (complementary biological irradiance spectra) creating high surface area, thin, flexible structures optimized for light trapping, and production of hydrogen (H2) from water, lignin, pollutants, or waste organics. We report a model coating system which produced 2.08 ± 0.01 mmol H2 m−2 h−1 for 4,000 h with nongrowing Rhodopseudomonas palustris, a purple nonsulfur photosynthetic bacterium. This adhesive, flexible, nanoporous Rps. palustris latex coating produced 8.24 ± 0.03 mol H2 m−2 in an argon atmosphere when supplied with acetate and light. A simple low-pressure hydrogen production and trapping system was tested using a 100 cm2 coating. Rps. palustris CGA009 was combined in a bilayer coating with a carotenoid-less mutant of Rps. palustris (CrtI) deficient in peripheral light harvesting (LH2) function. Cryogenic field emission gun scanning electron microscopy (cryo-FEG-SEM) and high-pressure freezing were used to visualize the microstructure of hydrated coatings. A light interaction and reactivity model was evaluated to predict optimal coating thickness for light absorption using the Kubelka-Munk theory (KMT) of reflectance and absorptance. A two-flux model predicted light saturation thickness with good agreement to observed H2 evolution rate. A combined materials and modeling approach could be used for guiding cellular engineering of light trapping and reactivity to enhance overall photosynthetic efficiency per meter square of sunlight incident on photocatalysts. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010

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