A scientist at North Carolina State University has received a $700,000 grant funded jointly by the US Departments of Energy (DOE) and Agriculture (USDA) to develop optimized versions of the eastern cottonwood tree (poplar) that can more easily be converted into ethanol.
The poplar is the only tree with a sequenced genome. (Earlier post.) Dr. Vincent Chiang wants to isolate the genes that regulate the manufacture of the three major components of wood: lignin, cellulose, and hemicelluloses.
Poplar’s extraordinarily rapid growth and its relatively compact genome size—480 million nucleotide units, 40 times smaller than the genome of pine—are among the many features that led researchers to target poplar as a model crop for biofuels production.
We want to understand at the genome level what controls the synthesis of the three major components of wood. If we can find the regulators that tell a tree to make more of one component and less of another, then we can engineer trees that are enriched with polysaccharides—a perfect feedstock for ethanol production.—Dr. Vincent Chiang
Cellulose and hemicelluloses are sugar polymers that can be converted into simple sugars, such as glucose, and then fermented to become ethanol. Collectively, cellulose and hemicelluloses are called polysaccharides. Wood is a great source of these polysaccharides— the substances represent approximately 70% of wood’s weight.
Extracting polysaccharides from wood or from any plant biomass is difficult because they are contained within lignin, a polymer that glues polysaccharides together to form wood. The lignin needs to be broken down with the use of acids or other substances, which makes extracting the polysaccharides challenging.
We have engineered trees with less lignin, and as a result we know that those trees are very useful for ethanol production. Now we’re interested in looking not just at genes that control lignin production, but at the genes that regulate how polysaccharides are made in wood.—Dr. Chiang