Breeding Better Biofuels
Nature’s design for trees works perfectly for photosynthesis, but not so well for biofuel production. The same stiffness in the wood cells that allows a tree to stand tall and catch as much sunlight as possible means extra processing steps to convert wood into ethanol—steps that add both cost and environmental risk. So Drs. Vincent Chiang and Ron Sederoff, co-directors of the Forest Biotechnology Group in the College of Natural Resources, are using a combination of genomics, bioinformatics, and biochemistry to design trees that are green in more ways than one.
“We really don’t need to create a strong tree for fuel as long as the tree can survive.”
Lignin, the glue-like polymer that makes wood stiff and strong, is the main obstacle to biofuel processing since, unlike the cellulose in wood, it doesn’t break down easily. Chemical pretreatments can filter out lignin, but they leave processors with a messy cleanup problem. Chiang studied the problem for two decades—first for the paper industry and now for the Department of Energy—and has identified the genes that control lignin production in fast-growing poplar trees. By manipulating these genes, he can produce poplars with up to 50 percent less lignin. Chiang says a 10 to 20 percent reduction would be an appropriate balance for producing biofuel without harming the tree. “We really don’t need to create a strong tree for fuel as long as the tree can survive.”
But consistently achieving that perfect blend of lignin and cellulose is a trickier matter. The Forest Biotechnology Group is experimenting with other genes, proteins, and metabolic pathways to learn more about how wood is formed and, in turn, how to get a better handle on lignin. “There’s a system of things regulating each other,” Sederoff says. “We’re looking at processes in a context larger than simple gene expression.” Rather than limit the lignin production, one such effort would change the chemical composition of the lignin that trees produce to make it easier to decompose.
Chiang and Sederoff are coordinating their research with Dr. Hou-min Chang of the Department of Wood & Paper Science to ensure the trees they’re creating work for biofuel production. They also have enlisted Dr. Dahlia Nielsen of the Bioinformatics Research Center to use their data to develop quantitative methods for breeding easily processed poplars. “Tree breeders don’t look at just one tree; they look at thousands,” Sederoff says. “We need to be able to harvest enough modified trees to make an impact in bioenergy.”