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Finding alternatives to corn-based ethanol is one of the major goals of Brookhaven’s biofuels research effort.The effort to identify and tailor new energy sources from plant products could go a long way towards addressing our nation’s future energy needs.
Plants are efficient energy scavengers, using sunlight to convert carbon dioxide and water into carbohydrates and other products that fuel every living thing on Earth. When we burn fossil fuels to generate heat or electricity, we tap into this ancient source of energy, locked up long ago by the plants and animals that decayed to form those fuels. But dwindling supplies, high costs, and environmental consequences of fossil fuels, such as global warming, have inspired scientists to explore how plants might fuel our future more directly.
One key strategy is the exploration of biofuels — fuels produced directly by plants or derived from plant materials such as stalks, stems, seeds, and fruits. To optimize biofuel production, scientists must gain a better understanding of how plants accumulate biomass and other products in ways that will enable them to influence these processes and convert the plant materials to renewable biofuels. With expertise in plant genetics, metabolism, molecular biology, chemistry, and environmental interactions, as well as access to a suite of high-tech tools, scientists at Brookhaven Lab are poised to make important contributions toward this goal and our nation’s sustainable energy future.
One of the best-known biofuels is ethanol, a form of alcohol produced by fermenting plant starches (e.g., corn), which can be used as a direct replacement for gasoline. But corn-based ethanol diverts an important food source — and the land it’s grown on — for fuel production. A better approach would be to find ways to use non-food crops, ideally ones grown on non-agricultural land, as the source for ethanol or other biofuel production.
Brookhaven researchers are actively investigating several plant species, including various grasses, aquatic plants such as duckweed, and fast-growing poplar trees. Poplar has adapted to many different climates and many different types of soil, including soil unfit for agricultural crops. Brookhaven researchers are looking for ways to increase these plants’ production of biomass and other products best suited for conversion to biofuels.
For example, through work originally designed to remove contaminants from soil, Brookhaven scientists have identified soil and plant-associated microbes that can improve plant growth on marginal soils. When bacteria equipped with the molecular “machinery” necessary to degrade environmental contaminants were introduced into poplar roots, the trees’ biomass production increased significantly, even when no contaminants were present.
Understanding such microbial-plant interactions may yield ways to further increase biomass. With the world’s largest collection of poplar-associated microbial species, Brookhaven stands to make significant advances in this area.
Another approach to improved biofuel production is to find ways to alter the composition of plant cell walls, the structural supports surrounding every plant cell. Like corn starch, plant cell walls can be broken down by enzymes into sugars suitable for fermentation into ethanol and other biofuels. But cell wall polymers (cellulose and hemicellulose) are much more difficult to “digest” than starch, making it necessary to find new enzymes for their efficient breakdown.
Using short- and long-lived radiotracers and sophisticated imaging technologies such as positron emission tomography and x-ray crystallography, Brookhaven scientists are exploring the factors that partition plant nutrients between production of lignin, a very recalcitrant cell wall compound, and hemicellulose and cellulose. The goal is to devise ways to tilt the balance toward more easily degraded cellulose, without compromising the structural integrity of the plants. Analysis of the plant enzymes involved in the production of cell wall materials, including structural studies at Brookhaven’s National Synchrotron Light Source, can help identify molecular targets and genetic engineering mechanisms for achieving this goal.
Radiotracer techniques are also being used to investigate the allocation of nutrients such as carbon and nitrogen within a plant, and to learn how to influence these processes to improve plants as resources for biofuel production. Unlike in food production, where the goal has been to get plants to grow bigger fruits, sometimes at the expense of the plant as a whole, the goal in biofuel production is to increase plant size overall and maximize carbon dioxide fixation.
Increasing the rate of plant growth may also have benefits for cell wall construction, because lignin takes more time to form than does cellulose. So finding ways to increase nutrient uptake rates would likely favor the production of more easily degraded cellulose and hemicellulose over hard-to-digest lignin. Microbes, again, might play a role here simply by increasing growth rates to tip the lignin/cellulose balance, or possibly by directly affecting the production of these different materials.
Last Modified: November 6, 2009