(672d) Factors Affecting the Enzymatic Digestibility of Dilute Acid Pretreated Corn Stover

Johnson, D. K. - Presenter, National Renewable Energy Laboratory
Adney, W. S. - Presenter, National Renewable Energy Laboratory
Ishizawa, C. - Presenter, National Renewable Energy Laboratory
Jeoh, T. - Presenter, National Renewable Energy Laboratory

A key barrier to the commercialization of fuels and chemicals produced from lignocellulosic biomass is the high cost and relative inefficiency of converting biomass into fermentable sugars. Dilute acid pretreatment is a promising technology for increasing the accessibility of cellulose to enzymatic hydrolysis. A better understanding of the interaction of enzymes with pretreated biomass is needed so that the rate and yields of sugars can be increased. Consequently, we continue to study the relationship between pretreatment conditions and the chemical and structural changes occurring in biomass during pretreatment. The purpose of this work was to uncover the factors that have the greatest influence in determining the enzymatic digestibility of the cellulose in dilute sulfuric acid pretreated corn stover. It has long been known that the removal of xylan greatly facilitates the enzymatic saccharification of the cellulose in biomass. It has been postulated that removal of lignin also increases digestibility. We have characterized a large set of dilute acid pretreated corn stover samples in which both xylan and lignin were removed to varying extents. All samples were treated at relatively high severities effecting >70% xylan removal. Additional modification of the samples to further decrease lignin content and/or change cellulose morphology was performed to examine how these affect cellulose digestibility. The crystallinity, particle size, porosity, cellulose degree of polymerization and cellulase binding of the samples was measured to determine the influence of these factors on the digestibility of the samples. It appears from this work that a change in cellulose morphology has the greatest potential for affecting cellulose digestibility.