Monday, April 30, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Lignocellulosic biomass pretreatment is an essential process in order to increase the conversion of biomass to ethanol and other products. Pretreatment of biomass reduces recalcitrance by improving accessibility of biomass to cellulases and other glycohydrolytic enzymes, which degrade biomass in a multi-step heterogeneous reaction at the liquid-solid interface. Understanding what changes occur in biomass during pretreatment, therefore, can elucidate leading factor(s) of recalcitrance, especially on the surface of the biomass where the interfacial layer during enzymatic deconstruction occurs. We employed Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) to perform chemical imaging of pretreated/deconstructed biomass at the submicron scale. Spatial changes of major components (e.g. cellulose and lignins) and their semi-quantitative variation on the surface of poplar stem biomass as detected by ToF-SIMS are compared to bulk composition data as obtained by HPLC before and after pretreatment. Following pretreatment, relatively more cellulose is observed on the surface of poplar stem biomass compared to bulk composition data, which suggest that there are chemical differences between surface and bulk. 3D microanalysis by ToF-SIMS has been applied to prove chemical differences from surface to sub-surface and to obtain lateral distribution of major components of pretreated biomass that can be related to the recalcitrance of biomass. Surface changes detected by ToF-SIMS images are also validated by other imaging approaches such as CARS (Coherent Anti-stokes Raman Scattering) microscopy and immune-fluorescence microscopy.