Characterization of the Interactions of Cellulose, Hemicellulose, and Lignin During Pretreatment Through the Use of Flowthrough Pretreatment

The conversion of lignocellulosic biomass to ethanol requires recovery of the sugars contained in hemicellulose and cellulose at high yields.  Hydrothermal pretreatment can be used to hydrolyze and solubilize hemicellulose prior to enzymatic hydrolysis of the cellulose left in the residual solids to glucose.  An understanding of the deconstruction of cell wall during pretreatment would support the development of improved energy crops and pretreatment strategies.  The results of flowthrough pretreatment of native poplar and model substrates were examined for evidence of the interaction of cellulose, hemicellulose, and lignin during pretreatment.  The liquid effluent was analyzed for oligomers and phenols, while the composition of the residual solids was tested using HPLC and NMR.  Differences in the release of xylooligomers from native poplar, holocellulose, and isolated xylan demonstrated the importance of the interactions of cellulose-hemicellulose and lignin-hemicellulose on hemicellulose hydrolysis.  Pretreatment of the isolated lignin indicates that depolymerization is the primary mechanism for lignin extraction while differences in the release of lignin from native poplar and the isolated lignin indicate that lignin-hemicellulose interactions influence relative reactivity.  Recent work has identified the removal of specific cell wall structures, such as methyl glucuronoxylan, as key to improvements in enzymatic digestibility.  The removal of these components during pretreatment will be examined closely.