Tuesday, April 20, 2010 - 3:00 PM
5-04

Lignin modification for biomass improvement- benefits and consequences

Richard A. Dixon, Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401

Economic and environmental factors favor the adoption of lignocellulosic bioenery crops for ethanol production. However, lignocellulosic biomass is recalcitrant to saccharification, and this is, at least in part, due to the presence of the phenylpropanoid-derived cell wall polymer lignin. Alfalfa is the major forage legume in the United States, and is also attracting interest as a bioenergy crop. Analysis of alfalfa plants in which lignin content and composition had been modified through independently down-regulating each of eight enzymes in the lignin pathway revealed that reduction in lignin content increased sugar release from dried biomass by both acid pre-treatment (hot sulfuric acid) and digestion by a cellulase mixture. Acid pre-treatment could effectively be omitted in the processing of biomass with the lowest lignin levels. However, the gains in fermentable sugar production are partially offset by reductions in plant yield in some, but not all, of these transgenic lines. This presentation will address the issues surrounding balancing agronomic performance in plants with altered cell wall properties. Potential mechanisms for pleiotropic effects of lignin modification will be discussed, and strategies for overcoming these effects outlined.

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