Monday, April 29, 2013
Exhibit Hall
A significant fraction of the xylooligomers (XOs) released by hydrothermal and low severity dilute sulfuric acid pretreatments at conditions that gave the highest overall sugar yields proved very recalcitrant to enzymatic hydrolysis. This study focused on characterization of these strongly recalcitrant XOs and their behavior in enzymatic hydrolysis to improve their conversion to xylose and other related products. The abilities of series of temperatures for precipitation, multi-step membrane Ultra filtration, and Gel permeation chromatography in separating XOs according to chain length was evaluated to select the most effective approach to isolate different DP fractions of hemicellulose oligomers prepared by both hydrothermal and dilute sulfuric acid pretreatments and characterize their behavior in hydrolysis. Conventional post-hydrolysis was applied to determine the xylose content in each DP fraction, and their purities were characterized by high performance anion-exchange chromatography and gel permeation chromatography. Hydrolysis kinetics were also determined for the most homogeneous XO fraction to better understand differences in breakdown patterns and identify if their recalcitrance to conversion was caused by xylose inhibition of enzymes, hydrolysis equilibrium, or differences or heterogeneity in oligomer bonds. Differences were also determined in the susceptibility of oligomers from hydrothermal and dilute sulfuric acid pretreatments to enzymatic hydrolysis.
Key words: xylooligomers characterization, kinetics, enzymatic hydrolysis, acidic hydrolysis