(134a) Elucidating Lignin Structure and Relationships from Naturally Variant Populus Trichocarpa

Lignocellulosic biomass is a promising renewable alternative to replace fossil fuels. The primary challenge to utilizing lignocellulosic material is its inherent recalcitrance to enzymatic hydrolysis. This recalcitrance is typically overcome by thermal and/or chemical pretreatment. Pretreatment performance is greatly influenced by lignin, a complex biopolymer. Therefore, it is important to understand the structure of native lignin. Due to its completely sequenced genome, it is possible to elucidate the genetic basis of lignin variation in Populus trichocarpa using phenotype-to-genotype correlation. To this effect, we have analyzed over 200 unique genotypes of Populus trichocarpa for lignin phenotype by HSQC NMR. This analysis has provided insights to the relative abundance and variation of syringyl, guaiacyl, p-hydroxyphenyl, and p-hydroxybenzoate units, as well as aryl ether, phenylcoumaran, and resinol linkages. Several correlations were also observed, such as syringyl:guaiacyl ratio to p-hydroxybenzoate units, aryl ether, and phenylcoumaran linkages. In addition, a gene expression analysis has identified 22 genes which are co-expressed with transcription factors known to impact cell wall biosynthesis. A variety of phenotypes, including phenotype extremes, are being further investigated for additional lignin properties such as molecular weight and antioxidant activity. Preliminary results suggest there may be a relationship between molecular weight and aryl ether linkages, as well as antioxidant activity and resinol linkages.