Production of poly-3-hydroxyalkanoates from CO and H2 by a novel photosynthetic bacterium |
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Authors: | Maness Pin-Ching Weaver Paul F |
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Institution: | 1.National Renewable Energy Laboratory, 80401, Golden, CO ; |
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Abstract: | A novel process is described to efficiently photoconvert low-grade organic materials such as waste biomass into natural biological
plastics. When heterogeneous forms of dry biomass are thermally gasified, relatively homogeneous synthesis gas mixtures composed
primarily of carbon monoxide and hydrogen are produced. Unique strains of photosynthetic bacteria were isolated that nearly
quantitatively photoassimilate the carbon monoxide and hydrogen components of synthesis gas into new cell mass. Under unbalanced
culture conditions when cellular growth is limited by shortages of nitrogen, calcium, magnesium, iron, or essential vitamins,
up to 28% of the new cell mass is found as granules of poly-3-hydroxyalkanoate (PHA), a highmolecular-weight thermoplastic
that can be solvent-extracted. The dominant monomeric unit of PHAs is 3-hydroxybutyrate (3HB), which is polymerized into the
homopolymeric poly-3-hydroxybutyrate (PHB). PHB is marketed as a biodegradable plastic with physical properties similar to
polystyrene. When a green alga was cocultured with the photosynthetic bacterium in light-dark (day-night) cycles, the bacteria
synthesized a polymer of poly-3-hydroxybutyrate-3-hydroxyvalerate (PHB-V) with a composition of 70% 3HB and 30% 3-hydroxyvalerate
(3HV) to an extent of 18% of the new cell mass. PHB-V is commercially marketed as Biopol and has physical properties similar
to polypropylene or polyethylene. Our results demonstrate that a strain of photosynthetic bacteria capable of photoassimilating
synthesis gas or producer gas is a potential candidate for large-scale production of biological polyesters. |
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Keywords: | Index Entries" target="_blank">Index Entries Biodegradable plastics poly-3-hydroxyalkanoates PHB-V Rhodobacter carbon monoxide |
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