3D Chemical Image using TOF-SIMS Revealing the Biopolymer Component Spatial and Lateral Distributions in Biomass

摘要

Many researchers consider biofuels, including bioethanol and biodiesel, as a resource to supplement or replace large portions of future transportation fuel requirements. This shift in research focus is due in part to limitations in fossil resources and recent concerns about the environment. Lignocellulosic biomass (for example, agricultural resides, forestry wastes, and energy crops) has been highlighted as a potential resource for biofuel production. Lignocellulosic biomass is mainly composed of polysaccharides (that is, cellulose and hemicelluloses) and lignin (polyphenolic macro-molecules). Cellulose, a major source of fermentable sugar used to produce ethanol, is known to be densely packed and embedded in a lignin-hemicellulose matrix. This intricate layering of lignin, cellulose, and hemicelluloses comprises the microstructure of biomass, and has to date not been fully identified. The structural complexity exhibited in lignocellu-lose originates from innate structural heterogeneity and has been suggested as a contributing factor in the its ability to resist enzymatic hydrolysis, which is referred to as biomass recalcitrance. Biomass recalcitrance has been cited as the major barrier to large-scale utilization of lignocellulosic biomass for biofuel production. Therefore, the major challenge facing future lignocellulosic biofuel research is reducing the recalcitrance of biomass through biological and chemical manipulation. For example, transgenic alfalfa down-regulated in lignin biosynthesis was shown to release more sugar by enzymatic hydrolysis. Thermochemical pretreatment using oxidizing, acidic, or basic conditions under high temperature and/or pressure results in structural cell wall breakdown along with changes in lignin and/or hemicelluloses, ultimately correlating with higher sugar release upon enzymatic hydrolysis.