Mutant Maize Genes May Help Harness Switch Grass for Biofuels
Mutant maize genes can be inserted into switch grasses to increase their viability as a biofuel crop, according to a study in the Proceedings of the National Academy of Sciences.
Transferring the so-called CG1 corn gene into switch grass can more than triple the amount of starch stored in the plant stems and make it easier to convert into the sugars needed for biofuels, researchers led by George Chuck at the University of California, Berkeley, said yesterday in the study.
The discovery may help make cellulosic ethanol output on a commercial scale cheaper and easier. Poet LLC, the largest U.S. corn-based-ethanol producer, BP Plc (BP/) and Abengoa SA (ABG) all plan U.S. factories by 2013. Gruppo Mossi & Ghisolfi began building a plant in Italy in April to make the fuel, a second-generation, or 2-G, biofuel, meaning it’s derived from non-food crops.
The grasses can yield as much as four times more sugar when treated with the mutant genes, which promote juvenile cell walls as the plant ages, the researchers found. The altered grasses didn’t flower, even after more than two years of growth, limiting the risk of the genetically modified variants spreading genes into the wild population.
“These results point to the potential utility of this approach, both for the domestication of new biofuel crops, and for the limitation of trans-gene flow into native plant species,” the researchers said.
Biofuels in Law
U.S. Congress passed a law in 2007 setting annual mandates for blending corn-based ethanol and cellulosic ethanol into gasoline every year through 2022. The Environmental Protection Agency had to lower the cellulosic mandates in 2010 and 2011 by more than 90 percent because the amount needed wasn’t available.
The enzymes needed to make 2-G biofuels cost about 50 cents a gallon, compared with 3 to 6 cents a gallon for ethanol from corn and sugar cane, Novozymes A/S Chief Executive Officer Steen Riisgaard said in February. That’s because a bigger volume of enzymes are required to break down the cellulosic material. The Danish company gets 18 percent of its revenue from enzymes for traditional biofuels, and less than 1 percent from 2-G, he said.
“Having extra starch may minimize the need for extensive pretreatment of the biomass,” the researchers wrote in the PNAS study. “Starch is much easier to digest compared with cellulose.”
Because the switch grasses grow on prairie terrain that’s unsuitable for corn, they don’t compete for land with food crops. Additional study is needed to ensure the genetic modification doesn’t make the grasses more susceptible to predators, the researchers said. They also said the discovery could be applied to other plants such as miscanthus grass and sorghum, to increase their viability as biofuel crops.
Chuck, the study’s lead author, also works for the U.S. Agriculture Department. The Joint BioEnergy Institute in Emeryville, California, contributed to the research.
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