In Washington state, researchers from the U.S. National Renewable Energy Laboratory announced that lignin-modified Eucalyptus trees developed by ArborGen releases more than twice the usual amount of sugar, making it a promising option as a biomass feedstock for liquid fuel. Using plant biotechnology the modifications were made at two points in the lignin biosynthetic pathway, with the largest increase in sugar release coming from cinnamate-4-hydroxylase (C4H) down-regulation.
Scientists from NREL have characterized the C4H lines as containing half the lignin of the unmodified lines. Using a high throughput sugar release assay developed at NREL (Selig et al, 2011 Biotech. Letters 1-7), the modified lines were found to release up to 99 percent of their sugars, up from 40 percent in the non-modified plants.
Although some “low recalcitrance” plant lines suffer from reduced growth, many of the C4H down-regulated lines from the E. grandis x E. urophylla cross grow well. C4H lines have an estimated biomass productivity of ten dry-tons per acre per year, with the potential to produce about 1,000 gallons of liquid biofuels per acre.