Advanced approaches for characterizing cell wall structure

Whereas plant cell walls have been measured by electron microscopy (EM) (13, 32-36), the drawback of EM techniques lies in the sample preparation and imaging processes commonly used, which involve chemical extraction, dehydration, and embedding. Because biomass samples go through both chemical pretreatment and enzymatic hydrolysis, methods must be developed to minimize the disruption of sample preparation, and conduct imaging under physiological conditions. Recently developed imaging methods, such as AFM, nonlinear optical microscopy, and single molecule methods, are capable of imaging the cell wall at nanoscale resolution without extensive sample preparation. These techniques can also be applied to directly map the macromolecular structures of cell walls, and to visualize their degrading enzymes simultaneously.