Chenlin Li1, Lan Sun1, Gang Cheng1, Michael Kent1, Venkatesh Balan2, Bruce Dale2, Blake Simmons1, and Seema Singh1. (1) Deconstruction Division, Joint BioEnergy Institute, Emeryville, CA 94608, (2) Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, MI
Pretreatment of lignocellulosic biomass is an essential step for biofuel production via biological routes. As one of the leading pretreatment techniques, ammonia fiber expansion (AFEX) has shown to decrease cellulose crystallinity and disrupt lignin-carbohydrate linkages. Recently, ionic liquids, a new type of non-volatile and green solvents, have demonstrated great promise for biomass dissolution, amorphous cellulose recovery and lignin rejection. However, to date, no comprehensive side-by-side comparative analysis has been conducted to evaluate AFEX and ionic liquid pretreatment processes. In addition, the mechanisms of how these two techniques cause the changes of substrate features, disrupt the intact cell-wall matrix, and impact on the subsequent enzymatic hydrolysis have not been researched well. To gain an in-depth understanding of both techniques, we compare AFEX and ionic liquid pretreatment acting on corn stover, evaluate their resultant saccharificaiton efficiency into fermentable sugars, and judge their feasibility for downstream biofuel production. The effects of both pretreatments on the cell-wall matrix and compositions are characterized and compared microscopically (confocal laser scanning microscopy) and spectroscopically (Fourier transform infrared and confocal Raman spectroscopy) at the molecular level. Small angle neutron scattering and X-ray diffraction are used to compare the porous and surface roughness as well as crystallinity on the nanometer length scale of corn stover before and after various pretreatments. These results provide new insights into the mechanisms of both pretreatments and indicate both are promising candidates for biomass pretreatment.
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