The Challenge of Redesigning Lignin for Biofuel Applications
Secondary cell walls of plants contain lignins that provide rigidity and pathogen resistance to the plant, but hinder breakdown of cell walls during biomass processing. This limits the efficient use of plants as bioenergy feedstocks. Lignins are polymers formed from several different chemical monomers and the nature of these monomers determines the properties of the lignin polymer. Modifying the lignin composition could significantly improve the ease of conversion of biomass to biofuel products, while retaining the critical functions of lignins for the plants growing in the field. Researchers at the DOE Great Lakes Bioenergy Center (GLBRC) have found that by altering two genes in Arabidopsis, a plant often used as a research model, a unique lignin is produced that contains a non-traditional monomer. The altered plant exhibits reduced lignin content, a trait desirable for increasing efficiency of deconstruction, but also shows aberrant growth and development and large metabolic shifts. The GLBRC researchers found evidence for genetic interactions between two lignin biosynthetic pathways. These results are an example of the type of unanticipated effects that will need to be taken into account when designing strategies for genetically engineering plant cell walls for bioenergy applications.
Vanholme, R., J. Ralph, T. Akiyama, F. Lu, J.R. Pazo, H. Kim, J.H. Christensen, B. Van Reusel, V. Storme, R. De Rycke, A. Rohde, K. Morreel, and W. Boerjan. 2010. “Engineering Traditional Monolignols Out of Lignin by Concomitant F5H1-up- and COMT-down-regulation in Arabidopsis,” Plant Journal. doe:10.1111/j.1365-313X.2010.04353.x.