Scientists Develop Aspen Trees with Altered Lignin for Better Biofuel Production

Lignin has been a problem for scientists interested in converting plant biomass to biofuels. A simple solution might be to engineer plants with less lignin, but previous attempts have often resulted in weaker plants and stunted growth. However, scientists at the U.S. Department of Energy's Brookhaven National Laboratory, together with their collaborators, have altered the lignin in aspen trees that resulted in increased access to sugars and ethanol yield, without affecting plant growth.

In the study, the scientists identified a variant of monolignol 4-O-methyltransferase, which can hinder the formation of a particular lignin component. The team then transplanted the gene for this variant into a strain of fast-growing aspen trees.

The transgenic trees had only slightly less total lignin in their cell walls. However, these trees also had altered, more condensed lignin structure. Scientists found that these condensed structures released up to 62 percent more simple sugars when treated with digestive enzymes.

Further analysis found that altering lignin content and composition also increased the production of cellulose fibers, the major source of fermentable sugars in the cell wall. This increased cellulose content might partially contribute to the increased release of simple sugars. Importantly, the changes did not affect the growth of the engineered aspens.