A key barrier to the commercialization of fuels and chemicals produced from lignocellulosic biomass is the high cost and relative inefficiency of converting biomass into fermentable sugars. Dilute acid pretreatment is a promising technology for increasing the enzymatic digestibility of lignocellulosic biomass. A better understanding of the pretreatability of biomass is needed so that the rate of formation and yields of sugars can be increased. Xylan is an important hemicellulosic component of the plant cell wall and acts as a barrier to cellulase access to cellulose. A key function of the dilute acid pretreatment process is the hydrolysis and solubilization of xylan so that cell wall sugars are available for subsequent fermentation. To better understand xylan hydrolysis in corn stover we have studied changes in the distribution of xylan caused by dilute acid pretreatment.

Samples of corn stover rind were labeled with a xylan antibody (LM11) that was conjugated with a fluorescent dye (Alexa Fluor488). Changes in the distribution of xylan were then monitored using laser scanning confocal microscopy. Samples were also labeled with another xylan antibody (LM10) that was conjugated with a gold nanoparticle. After subsequent gold enhancement, xylan distribution within the cell wall could be visualized by scanning electron microscopy. Our studies have focused on the sclerenchyma cells near the vascular bundles for consistency in imaging and because these cells also contain the largest amounts of mass. After pretreatment the xylan antibody signal was observed to decrease in the bulk of the primary and secondary cell walls while the signal in the middle lamella and lumen was maintained and possibly even increased. It is possible that these changes in xylan distribution may be related to the biphasic kinetic behavior that has been reported for xylan hydrolysis rates.