|GTL Science and Technology Foundations for DOE Missions.|
The Department of Energy (DOE) today issued a comprehensive plan for a new generation of biological research that builds on genome project investments to tackle national energy and environmental challenges.
The Genomics: GTL (Genomes to Life) Roadmap—Systems Biology for Energy and Environment outlines a plan to explore the potential of microbes—starting with information encoded in their DNA sequences—for achieving cleaner and more secure energy resources, remediating toxic wastes and understanding the natural roles microbes play in the global climate.
Much as the Human Genome Project [also funded by DOE] stimulated the growth of a biomedical biotechnology industry, the research laid out in this roadmap will spur growth in a new industrial biotechnology sector. Microbes can be used for processes and products that can serve as an engine for economic competitiveness in the 21st century.—Secretary of Energy Samuel W. Bodman
The roadmap traces the path from national energy and environmental needs to the scientific progress that should be pursued with the benefit of emerging technologies, integrated computing and a new research infrastructure. The new plan was formulated over the last three years with the expertise of nearly 800 scientists and technology experts and is now being reviewed and refined at the National Academy of Sciences.
The GTL research program has three phases. In the first phase (Genomics to Systems Biology), key proof of principle experiments on complex energy and environmental systems will be performed and new technologies and computing techniques will be developed, used for science and scaled up in user research facilities.
In the second phase (Technology Integration and Setup), the high throughput tools and capabilities will be applied to rapidly understanding biological processes, developing concepts for industrial application to energy and environmental problems and to understand the interactions between global biological processes and climate.
In the third and final phase (Biological Systems Knowledge for DOE Applications), this knowledge and these capabilities will position GTL to rapidly transform new science into new processes and products to help meet critical national energy and environmental needs.
With respect to the energy mission of the DOE, GTL mission is to “provide a systems-level understanding of biological processes for developing and deploying large-scale, environmentally sound biotechnologies to produce biofuels and other high-value chemical products that reduce dependence on foreign energy sources and enhance national economic prosperity.”
While the roadmap leaves open development in a variety of area, such as the biotechnological development of commercial chemical processes for plastics and chemical production, it is especially focused on two areas of applied research in bioenergy: ethanol from biomass (bioethanol) and biohydrogen.
For bioethanol, GTL will focus on accelerating the development of optimal cellulase systems by providing resources for screening thousands of natural and modified enzyme variants, enabling the high-throughput production and functional analysis of these enzymes, elucidating regulatory controls and essential molecular interactions, and developing models for analyzing the structure and activity of natural and engineered enzyme systems.
A long-term target for GTL research is integrated bioprocessing, or the conversion of biomass to ethanol in a single step. Accomplishing this requires the development of a genetically modified, multifunctional organism or a stable mixed culture capable of carrying out all biologically mediated transformations needed for the complete conversion of biomass to ethanol.
The GTL roadmap also calls out for special consideration the biophotolysis of water to hydrogen—the use of green algae and cyanobacteria to use a water-splitting photosynthetic processes to generate molecular hydrogen.
Biophotolysis holds potential for the scale of hydrogen production necessary to meet future energy demand. This approach to hydrogen production is promising because the source of electrons or reducing power required to generate hydrogen is water—a clean, renewable, carbon-free substrate available in virtually inexhaustible quantities. Another advantage of biophotolysis is the more efficient conversion of solar energy to hydrogen.
Reengineering microbial systems for the direct production of hydrogen from water eliminates inefficiencies associated with carbon fixation and biomass formation. Theoretically, the maximal energetic efficiency for direct biophotolysis is about 40% (Prince and Kheshgi 2005) compared with a maximum of about 1% for hydrogen production from biomass (Hydrogen Economy 2004).
Recognizing the important potential of biophotolysis, NRC has recommended that DOE “refocus its bio-based program on more fundamental research on photosynthetic microbial systems to produce hydrogen from water at high rate and efficiency” (Hydrogen Economy 2004).
The roadmap calls out four areas of focus for biohydrogen:
Engineering Oxygen-Tolerant, Efficient Hydrogenases. Hydrogenases known to tolerate oxygen generally are not very efficient hydrogen producers. During biophotolytic hydrogen production, oxygen is released from the water-splitting reaction, thus engineering hydrogenases with sufficient activity and oxygen tolerance will be needed. Engineered hydrogenases then could be used in bioinspired nanostructures that maintain optimal conditions for hydrogen production.
Designing Microorganisms Optimized for Hydrogen Production. Photosynthetic microbes that have been genetically modified to produce hydrogen at high rates and efficiency from the biophotolysis of water could be grown in extensive farms of sealed enclosures (photobioreactors). Hydrogen would be harvested for use in energy applications, with oxygen released as a by-product.
Nitrogenase-Mediated Hydrogen Production. In the absence of oxygen and presence of light, purple nonsulfur (PNS) photosynthetic bacteria such as Rhodopseudomonas palustris and Rhodobacter sphaeroides contain nitrogenase enzymes that can generate hydrogen under nitrogen-limited conditions. These microbes obtain the electrons they need to reduce protons to molecular hydrogen from the breakdown of organic compounds. Certain species of cyanobacteria also contain nitrogenase enzymes capable of producing hydrogen as a by-product of nitrogen fixation.
Fermentative Hydrogen Production. A variety of bacteria such as E. coli, Enterobacter aerogenesEnterobacter aerogenes, and Clostridium butyricum are known to ferment sugars and produce hydrogen using multienzyme systems. These “dark fermentation” reactions do not require light energy, so they are capable of constantly producing hydrogen from organic compounds throughout the day and night. Compared with other biological hydrogen-production processes, fermentative bacteria have high evolution rates of hydrogen. However, sugars are relatively expensive substrates that are not available in sufficient quantities to support hydrogen production at a scale required to meet energy demand.
There are massive gaps in scientific understanding in all these areas. The technical challenges presented by GTL analyses and the scale of the systems that must be understood—from genomes to ecosystems—exceed current capabilities. To meet these analytical needs, DOE has proposed four large research and production facilities for rapidly unraveling the tremendous complexity of biological systems. The facilities are:
Facility for Production and Characterization of Proteins and Molecular Tags
Facility for Characterization and Imaging of Molecular Machines
Facility for Whole Proteome Analysis
Facility for Analysis and Modeling of Cellular Systems
These resources would be available to the broader research community as well as industry and would dramatically increase the pace of discovery. Such advances will enable rapid translation of science into new technologies, ultimately shortening the path to national benefits. The GTL facilities are among those featured in the DOE Office of Science’s 20-year facilities plan (Facilities for the Future of Science: A Twenty-Year Outlook, 2003).
The 2005 GTL Roadmap builds on and expands the GTL research program begun in 2002. Scientific and technological progress achieved during the Human Genome Project, initiated in 1986 by DOE, and the Microbial Genome Program, begun in 1994, provided the foundation for establishing the GTL program.