Monday, May 2, 2011
Grand Ballroom C-D, 2nd fl (Sheraton Seattle)
The kinetics of xylan hydrolysis appears to be governed by two parallel first-order reactions with one reaction much faster than the other. Our goal was to determine if this apparent biphasic hydrolysis was due, either fully or partially, to structural characteristics in plant cell walls. Dilute acid pretreatment experiments performed where lignin was removed either before or during pretreatment were expected to remove or at least significantly diminish the biphasic kinetic effect. Dilute acid pretreatment of corn stover (CS) delignified under mild conditions still exhibited biphasic kinetics, although the fraction of slow hydrolyzing xylan decreased and the overall rate of xylan hydrolysis increased. Pretreatment of CS under organosolv conditions, where xylan and lignin are solubilized simultaneously, also appeared to exhibit biphasic xylan hydrolysis kinetics. The solubilization of xylan and lignin appeared to occur at similar rates. The raw and pretreated CS samples were treated with a monoclonal antibody that binds xylan specifically so that the location of xylan in the cell wall could be imaged by confocal laser scanning microscopy (CLM). CLM of the pretreated delignified samples showed a similar intense signal pattern as exhibited by raw and pretreated control samples. The bright signal indicating that the majority of the remaining xylan was located at the cell wall edges. CLM of the organosolv pretreated CS did, however, show a diminution in signal intensity at the cell wall edges compared to CS pretreated under standard dilute acid conditions.