Lignin is a major component of plant cell wall besides cellulose and hemicellulose. Structurally lignin is linked with hemicelluloses and cellulose to form recalcitrant complex that resist the attack by hydrolytic enzymes. Overcoming the recalcitrance of lignocellulosic biomass is considered as a major barrier for bio-refinery. Aiming to increase efficiency of carbohydrate saccharification, many efforts have been made to remove and/or modify lignin moieties. Biological degradation of lignocellulosic biomass is an integral part of the ecosystem function. However, due to the limitation of our knowledge on detection and quantification of lignin unit at structural level, the relationship between structural changes resulted from biological actions and associated impact on cellulase function is still unclear. In order to unveil the natural degradation mechanisms on ligninocellulosic biomass, Milled wood lignin (MWL) and cellulolytic enzyme-treated lignin (CEL) isolated from bio-degraded of wheat straw by Phanerochaete chrysosporium were comprehensively explored to determine their structural integrity and dynamics in cellulase adsorption. A quantitative method was developed to characterize wheat straw lignin subunits by combination of quantitative 13C NMR and HSQC 2D NMR techniques. In addition to common syringyl, guaiacyl and p-hydroxyphenol units, various units and side chains including �-O-4, dibenzodioxocin, phenylcoumaran, pinoresinol, spirodienone ferrulate, coumarate and p-benzonate were identified and quantified. The results showed that P. chrysosporium caused significant lignin modification. Detail structural dissection revealed significant reduction in S/G ratio and hydroxycinamate/lignin ratio in secondary cell wall. This study suggested that a preferential degradation of phenolic interlinks connecting cell wall carbohydrates seemed to be a unique mechanism of lignin modification and cellulose hydrolysis caused by this fungus.

New evidences in wheat straw cell wall deconstruction by <i>Phanerochaete chrysosporium</i>

245th National Meeting (2013)

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New evidences in wheat straw cell wall deconstruction by Phanerochaete chrysosporium