Berkeley Lab team creates “cyborgian” hybrid artificial photosynthesis system; CO2 to acetic acid at high yield
05 January 2016
Researchers at Berkeley Lab have induced the self-photosensitization of a nonphotosynthetic bacterium—Moorella thermoacetica—with cadmium sulfide nanoparticles (M. thermoacetica–CdS), enabling the photosynthesis of acetic acid from carbon dioxide.
Their hybrid approach combines the highly efficient light harvesting of inorganic semiconductors with the high specificity, low cost, and self-replication and -repair of biocatalysts. Biologically precipitated cadmium sulfide nanoparticles served as the light harvester to sustain cellular metabolism. This self-augmented biological system selectively produced acetic acid continuously over several days of light-dark cycles at relatively high quantum yields, demonstrating a self-replicating route toward solar-to-chemical CO2 reduction. A paper on their work is published in Science.
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| M. thermoacetica–CdS reaction schematics. (A) Depiction of the M. thermoacetica–CdS hybrid system, proceeding from the growth of the cells and bioprecipitation (loading) of the CdS nanoparticles (shown in yellow) through photosynthetic conversion of CO2 (center right) to acetic acid (right). (B) Pathway diagram for the M. thermoacetica–CdS system. Two possible routes to generate reducing equivalents, [H], exist: generation outside the cell (dashed line) or generation by direct electron transport to the cell (solid line). Credit: AAAS, Sakimoto et al. Click to enlarge. |
We’ve demonstrated the first self-photosensitization of a non-photosynthetic bacterium, M. thermoacetica, with cadmium sulfide nanoparticles to produce acetic acid from carbon dioxide at efficiencies and yield that are comparable to or may even exceed the capabilities of natural photosynthesis.
The bacteria/inorganic-semiconductor hybrid artificial photosynthesis system we’ve created is self-replicating through the bio-precipitation of cadmium sulfide nanoparticles, which serve as the light harvester to sustain cellular metabolism. Demonstrating this cyborgian ability to self-augment the functionality of biological systems through inorganic chemistry opens up the integration of biotic and abiotic components for the next generation of advanced solar-to-chemical conversion technologies.
—Peidong Yang, a chemist with Berkeley Lab’s Materials Sciences Division, who led this work
Artificial versions of photosynthesis are being explored for the sustainable production of chemical products now made from petroleum—primarily fuels and plastics. Yang and his research group have been at the forefront of developing artificial photosynthetic technologies that can realize the full potential of solar-to-chemical synthesis.
Cadmium sulfide is a well-studied semiconductor with a band structure and that is well-suited for photosynthesis. As both an “electrograph” (meaning it can undergo direct electron transfers from an electrode), and an “acetogen” (meaning it can direct nearly 90% of its photosynthetic products towards acetic acid), M. thermoacetica serves as an ideal model organism for demonstrating the capabilities of this hybrid artificial photosynthesis system.
Biological routes to solid-state materials have often struggled to compete with high-quality traditionally synthesized materials. This work demonstrates not only that biomaterials can be of sufficient quality to carry out useful photochemistry, but that in some ways they may be more advantageous in biological applications.
… The M. thermoacetica–CdS system displays behavior that may help it to exceed the utility of natural photosynthesis. First, the quantum yield increased with higher M. thermoacetica–CdS concentrations. The ability to tune the effective light flux per bacterium by changing the concentration of the suspension is a considerable advantage over similar light management practices in natural photosynthesis that are achieved through genetic engineering of chloroplast expression. Second, the catabolic energy loss observed during dark cycles in natural photosynthesis was absent in our hybrid system, which may be an innate feature of the Wood-Ljungdahl pathway, in which acetic acid is a waste product of normal respiration. Additionally, many plants and algae tend to store a large portion of their photosynthetic products as biomass, which requires extensive processing to produce useful chemicals. In contrast, the M. thermoacetica–CdS system directs ~90% of photosynthetic products toward acetic acid, reducing the cost of diversifying to other chemical products.
—Sakimoto et al.
This work was funded by the US Department of Energy (DOE)’s Office of Science. The interface design part of the study was carried out the Molecular Foundry, a DOE Office Science User Facility hosted by Berkeley Lab.
Resources
Kelsey K. Sakimoto, Andrew Barnabas Wong, Peidong Yang (2016) “Self-photosensitization of nonphotosynthetic bacteria for solar-to-chemical production” Science Vol. 351 no. 6268 pp. 74-77 doi: 10.1126/science.aad3317
There is not enough land area in NYC to supply the fuel it needs from the sun. Even if Long Island were added with more area but also more demand, there would still not be enough, and the people would not like every bit of land covered with solar collectors not for their own use even if they were plants.
The common trick of solar renewable energy proponents is that they multiply the surface of the earth by the solar energy impinging upon it and declare that there is more than enough without stating the efficiency of the collectors and the costs in land, materials, and labour in collecting it and distributing it. They also forget that clouds exist and avoid the mention that night and seasons multiply the collection costs and ignore the storage costs. The costs and inefficiencies of collecting solar energy from the oceans and polar regions is never mentioned in statements; as are not the damages to the ecosystem including all known and unknown organisms.
Hydrogen is the fossil fuel of the sun, and it could be collected in great quantities from some of the large planets and turn all of the oxygen in the air of the earth to water and the CO2 to wax and water.
Every bit of matter on the earth is fossil material from exploding or burning stars or the creation of the universe and very little of it is going to leave this planet and much more comes in as space dust and chunks.
All materials upon the earth are fossils and there are not enough of them for enormous populations, but there are enough quantities of uranium and thorium on land and in the oceans to supply all of the people on earth with many times the average of the energy consumption per person in the UK for billions of years. This means all direct and indirect uses. This includes all of the energy needed to grow and harvest and preserve and transport food as well as all of the energy needed to synthesize food and gather the elements to do so. ..HG..
Posted by: Henry Gibson | 11 January 2016 at 12:38 AM