Monday, April 30, 2007

Lignin redeposition on lignocellulosic biomass during pretreatment under neutral and acidic conditions

Michael J. Selig, Sridhar Viamajala, Todd B. Vinzant, Melvin P. Tucker, and Stephen R. Decker. National Renewable Energy Laboratory, 1617 Cole. Blvd MS 3323, Golden, CO 80401

Electron microscopy of lignocellulosic biomass after high temperature pretreatment has revealed the presence of spherical bodies on the surface of the residual biomass.  Although this is not a novel observation, little work has been carried out to determine the cause and effect of this phenomenon.  Experiments were run in order to better understand the nature of these structures during the pretreatment process and possible implications their existence may have on the enzymatic saccharifcation of cellulose present in pretreated biomass. Preliminary evidence points towards lignin as the major component of this material, though polysaccharides and other compounds may be present.  It was demonstrated that these “lignin” droplets are produced from biomass during pretreatment under acidic and neutral pH at temperatures above 130oC, and that these droplets can redeposit onto the cellulose surface. Investigations into the chemical nature of this adhesion revealed that hydrogen bonding might play a role in the interactions between the droplets and cellulose. The interaction with cellulose was shown to negatively effect the enzymatic saccharification of an artificial cellulose substrate under certain pretreatment conditions, indicating that the redeposition of this material has the potential to adversely effect the enzymatic conversion of cellulose in pretreated biomass.