284882 Plausible Implications of Hemicellulose Precipitation On Cellulose Digestibility for Hydrothermal and Low Severity Dilute Acid Pretreatments of Cellulosic Biomass

Thursday, November 1, 2012: 9:45 AM
335 (Convention Center )
Rajeev Kumar1,2 and Charles Wyman2,3, (1)Center for Environmental Research and Technology, University of California, Riverside, Riverside, CA, (2)BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, (3)Chemical and Environmental Engineering, University of California Riverside, CE-CERT, Riverside, CA

Cellulose digestion in lignocellulosic biomass prepared by hydrothermal and low severity dilute acid pretreatments at low enzyme loadings is typically low. Protective hemicellulose sheathing and cellulase inhibition by hemicellulose xylooligomers released during enzymatic hydrolysis are often considered to contribute to the low cellulose digestion for such pretreatments. However, based on earlier studies in our lab on xylan/ xylooligomers solubilization and current understandings, we propose a novel hypothesis that hemicelluloses during hydrothermal and low severity dilute acid pretreatments move out of the plant cell wall into solution and precipitate onto the biomass during pretreatment and/or upon cooling.  They can then form strong bonds with cellulose and/or lignin that are different from natural linkages, resulting in less digestible cellulose. Therefore, in this study, we investigated the effects and underlying mechanisms of hemicellulose precipitation on cellulose digestibility for hydrothermal and low severity dilute acid pretreatments of pure cellulose mixed with pure hemicellulose compounds. The results of pretreating Avicel mixed with xylan showed a remarkably lower digestibility than an Avicel control, and the drop in cellulose digestion was much greater than realized when xylan at similar or higher concentrations was physically mixed with Avicel.

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See more of this Session: Advances In Biofuels: DOE Bioenergy Research Centers I
See more of this Group/Topical: Sustainable Engineering Forum