Quantitative chemical imaging of lignin species in biomass and their behavior in pretreatment and enzyme hydrolysis

A biochemical platform holds the most promising route toward lignocellulosic biofuels, in which polysaccharides are hydrolyzed by cellulase enzymes into simple sugars and fermented to liquid fuels by microbes. However, these polysaccharides are cross-linked in the plant cell walls with the hydrophobic network of lignin that physically impedes enzymatic deconstruction. A thermochemical pretreatment process is often required to remove or delocalize lignin, which may also generate inhibitors that hamper enzymatic hydrolysis and fermentation. Our recent development of micro-spectroscopy enables correlative nanoscale imaging, in situ chemical mapping and in vivo molecular tracking at the cellular and single molecule scales. We will report our studies on identifying different physicochemical properties of lignin species in the plant cell walls and their behaviors during pretreatment and enzyme hydrolysis using non-destructive and quantitative imaging approaches (Zeng et al., 2014 Curr. Opin. Biotechnol.; Ding et al., 2012, Science).  Perspectives and future directions to improve the biomass conversion process will also be discussed.