AUTHOR=Ragauskas Arthur , Pu Yunqiao , Samuel Reichel , Jiang Nan , Fu Chunxiang , Wang Zeng-Yu 

TITLE=Structural Characterization of Lignin in Wild-Type versus COMT Down-Regulated Switchgrass

JOURNAL=Frontiers in Energy Research

VOLUME=1

YEAR=2014

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2013.00014

DOI=10.3389/fenrg.2013.00014

ISSN=2296-598X

ABSTRACT=<p>This study examined the chemical structural characteristics of cellulolytic enzyme lignin isolated from switchgrass focusing on comparisons between wild-type control and caffeic acid 3-<italic>O</italic>-methyltransferase (COMT) down-regulated transgenic line. Nuclear magnetic resonance techniques including <sup>13</sup>C, <sup>31</sup>P, and two-dimensional <sup>13</sup>C-<sup>1</sup>H heteronuclear single quantum coherence as well as gel permeation chromatography were employed. Compared to the wild-type, the COMT down-regulated transgenic switchgrass lignin demonstrated a decrease in syringyl (S):guaiacyl (G) ratio and <italic>p</italic>-coumarate:ferulate ratio, an increase in relative abundance of phenylcoumaran unit, and a comparable content of total free phenolic OH groups along with formation of benzodioxane unit. In addition, COMT down-regulation had no significant effects on the lignin molecular weights during its biosynthesis process.</p>