Characterization and Quantification of Monomers, Oligomers and By-Products from Hemicellulose during Pretreatment

University Of Arkansas, Fayetteville AR

Investigators

Abstract

CBET-0828875 Carrier Intellectual Merit: The goal of this project is to analyze and characterize aspects of hemicellulose used during pretreatment in the production of ethanol. The PI ultimately seeks to help reduce ethanol production costs by economically converting both the hemicellulose and cellulose sugars. In this project, the PI focuses on the hemicellulose depolymerization aspect versus cellulose conversion, which has been highly researched in the past. Hemicellulose represents 20-40% of the lignocellulosic biomass used in ethanol production. If completely depolymerized without sugar degradation, the hemicellulose depolymerization could increase the current productivity of lignocellulosic conversion to ethanol by at least 15%. Hemicellulose depolymerization is not a simple task. Depolymerization of hemicellulose in the presence of dilute acid or hot water forms a host of previously uncharacterized oligomers, as well as desired sugar monomers and undesirable degradation products such as furfural. This particular research will produce and characterize xylan-derived and switchgrass-derived hemicellulose oligomers; determine whether these oligomers depolymerize as conceptualized in the literature; and determine dissociation constants for oligomer depolymerization and monomer degradation in the development of a probabilistic model describing monomer formation. The PI will purchase xylan but will also extract hemicellulose from switchgrass. By monitoring the depolymerization of the individual oligomers, the PI will calculate dissociation rate constants and will generate a model describing the depolymerization of oligomers through Bayesian analysis. This model will be used to predict the operating conditions that minimize inhibitory by-product formation. The PI also seeks to identify the mechanisms by which hemicellulose depolymerizes to five- and six-carbon carbohydrate monomers providing better fundamental understanding of cell wall breakdown in the biomass to liquid fuels conversion process. This research will characterize the mechanisms by which monomers are released from these oligomers. Characterization of the kinetics of oligomer conversion to xylose is crucial because monomeric xylose can yield furfural, a by-product which must be eliminated, or at least minimized. Broader Impact: This research focuses on important aspects in energy, environmental and educational fields. The results of this work will address the issues of energy sustainability by maximizing the potential that lignocellulosic material offers as a feedstock for energy production. Additionally, through this research, the PI will educate two PhDs and several undergraduate students, including students from underrepresented groups, in sustainable energy engineering.