(Science Magazine) Addition by subtraction. By removing a specific gene, researchers reduced the amount of lignin (stained red) by 36% in cells in a plant’s stem, making it easier to recover sugar-rich parts of the plant that can be converted to automotive fuel. If the same technique works in biofuel crops such as poplar trees (inset) it could sharply reduce the cost of making biofuels.
Wood is strong, abundant, and cheap. But when it comes to the hot prospect of turning trees and agricultural waste into an energy source for cars and trucks, wood gets in the way. Now, scientists say they’ve found a possible solution to this difficulty, one that could dramatically reduce the cost of tomorrow’s fuels.
The problem with wood is a component in its cell walls known as lignin, which confers rigidity. Engineers must first remove the lignin to get to the sugar-rich cellulose in plants, which they ferment into alcohol-based fuel. Researchers have been looking for ways to reduce the amount of lignin in trees and plants without harming their ability to grow.
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So Boerjan (Wout Boerjan, a molecular geneticist at Ghent University in Belgium) and his colleagues ran genetic screens of the genes expressed in Arabidopsis thaliana, a small plant commonly studied in biological laboratories. When the researchers determined which genes were active in plants that were making lignin, they noticed one that hadn’t been identified as central to lignin biosynthesis, a gene for an enzyme called caffeoyl shikimate esterase (CSE). They then engineered Arabidopsis plants so they didn’t have theCSE gene. As the researchers report online today in Science, the plants still grew. But they contained 36% less lignin and were about a third smaller than their unaltered counterparts. They also didn’t droop or fall over, though some of their vessels for transporting food and water collapsed. Still, when the shorter plants were dried, cut up, and processed, they yielded four times the amount of sugar-rich cellulose as did the unaltered plants. What’s more, they gave up this extra cellulose without the expensive high-temperature processing usually required to remove the lignin prior to fermenting biofuels. READ MORE and MORE (Scientific American) and MORE (MIT Technology Review)