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
Rapid adaptation to a changing environment
28.04.2016 | Christian-Albrechts-Universität zu Kiel
Tiny microscopes reveal hidden role of nervous system cells
28.04.2016 | Salk Institute
Neutron scattering and computational modeling have revealed unique and unexpected behavior of water molecules under extreme confinement that is unmatched by any known gas, liquid or solid states.
In a paper published in Physical Review Letters, researchers at the Department of Energy's Oak Ridge National Laboratory describe a new tunneling state of...
Honeycomb structures as the basic building block for industrial applications presented using holo pyramid
Researchers of the Alfred Wegener Institute (AWI) will introduce their latest developments in the field of bionic lightweight design at Hannover Messe from 25...
Polymer solar cells can be even cheaper and more reliable thanks to a breakthrough by scientists at Linköping University and the Chinese Academy of Sciences (CAS). This work is about avoiding costly and unstable fullerenes.
Polymer solar cells can be even cheaper and more reliable thanks to a breakthrough by scientists at Linköping University and the Chinese Academy of Sciences...
As one of the leading R&D partners in the development of surface technologies and organic electronics, the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP will be exhibiting its recent achievements in vacuum coating of ultra-thin glass at SVC TechCon 2016 (Booth 846), taking place in Indianapolis / USA from May 9 – 13.
Fraunhofer FEP is an experienced partner for technological developments, known for testing the limits of new materials and for optimization of those materials...
Liquid water is a very good heat storage medium – anyone with a Thermos bottle knows that. However, as soon as water boils or freezes, its storage capacity drops precipitously. Physicists at the University of Bonn have now observed very similar behavior in a gas of light particles. Their findings can be used, for example, to produce ultra-precise thermometers. The work appears in the prestigious technical journal "Nature Communications".
Water vapor becomes liquid under 100 degrees Celsius – it condenses. Physicists speak of a phase transition. In this process, certain thermodynamic...
27.04.2016 | Event News
15.04.2016 | Event News
12.04.2016 | Event News
28.04.2016 | Physics and Astronomy
28.04.2016 | Materials Sciences
28.04.2016 | Life Sciences