Fuel cells are a highly promising means of producing electricity. However, the hydrogen they require is still largely obtained from coal, oil, or natural gas. Producing hydrogen from less expensive biomass is an attractive alternative, but has not produced sufficient yields to date.
In the journal Angewandte Chemie, a team of American and Mexican researchers has now introduced a cell-free biosystem of thirteen enzymes that can produce hydrogen from xylose, one of the main components of plants, in yields of over 95 %.
Xylose is a pentose (a sugar molecule containing five carbon atoms), and is one of the main building blocks of lignocellulosic biomass—wood and parts of woody plants. It is not economically feasible to separate xylose from the other components of biomass for the production of hydrogen. There are microorganisms that can convert xylose and glucose, the building block that makes up cellulose, into hydrogen. However, the yields are very low.
Y.-H. Percival Zhang at Virginia Tech (Blacksburg, USA) and his co-workers in the USA and Mexico have thus resorted to a trick: They are using the enzymes used by the microorganisms, but in a cell-free system. They combined thirteen enzymes and various cofactors like NADPH into a complex cascade that do not exist in the natural metabolic systems. In a bioreactor, they were able to produce hydrogen from xylose with a yield of over 95 %.
The downside: In the first step of the reaction, xylose is isomerized into xylulose, which must be activated in a second step by addition of a phosphate group. This requires ATP (adenosine triphosphate), the "energy carrier" of cells, to "pump" chemical energy into the enzyme cascade. Unfortunately, ATP is a very expensive material. The thing that depends on ATP is the splitting of the energy-rich bonds between individual phosphate groups. The researchers thus had an idea: They wanted to replace the ATP with a more economical substance, polyphosphate, which also contains energetic phosphate bonds. However, this requires a xylulokinase, an enzyme that attaches phosphate groups to xylulose, and can use polyphosphate instead of ATP.
Polyphosphate is found in volcanic rocks and in deep-oceanic steam vents. Primeval organisms may have used this substance. The researchers isolated the gene for a xylulokinase from thermotoga maritima, a thermophilic microorganism found in such environments, and used genetic engineering to produce the enzyme. As they hoped, this enzyme can also use polyphosphate and can successfully replace the ATP-dependent xylulokinase in the enzyme cascade.
This team had previously developed a synthetic enzymatic route for the production of hydrogen from cellulose. Now both of the major components of biomass, cellulose and xylose, can be converted together in a new approach for the more economical production of hydrogen.About the Author
Author: Y.-H. Percival Zhang, Virginia Tech, Blacksburg (USA), http://filebox.vt.edu/users/ypzhang/zhang.htm
Title: High-Yield Production of Dihydrogen from Xylose by Using a Synthetic Enzyme Cascade in a Cell-Free System
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201300766
Y.-H. Percival Zhang | Angewandte Chemie
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering