10-03: Effect of pretreatment on biomass structure and cellulose properties

The structure and chemical composition of plant biomass has evolved to make the cellulose recalcitrant to hydrolysis by cellulase enzymes. Contributing factors to the recalcitrance of lignocellulosic biomass include cell structure, liquid penetration into the plant cell wall, hemicellulose and cellulose chemical structures, and lignification. Enzymatic conversion of lignocellulosic biomass requires an effective pretreatment to enable efficient cellulase penetration into the plant cell wall through to the cellulose microfibrils. Dilute acid pretreatment substantially increases the accessibility of the cellulose to hydrolytic enzymes and decreases the recalcitrance of the cellulose to hydrolysis. Using a variety of tools, we have developed a better understanding of how the pretreatment process affects biomass structure and cellulose properties that impact on its digestibility. Characteristics such as cellulose accessibility, crystallinity, morphology and molecular weight are monitored to ascertain the effects of pretreatment on the cellulose, in addition to other factors including substrate porosity and particle size. Microscopic imaging can indicate changes in lignin and xylan distribution in the plant cell wall that are also important.