Title page for ETD etd-11142011-033105


Type of Document Dissertation
Author Sathitsuksanoh, Noppadon
Author's Email Address sathino@vt.edu
URN etd-11142011-033105
Title Lignocellulose Saccharification via Cellulose Solvent Based Fractionation Followed by Enzymatic Hydrolysis: the Last Obstacle to Integrated Biorefineries
Degree PhD
Department Biological Systems Engineering
Advisory Committee
Advisor Name Title
Zhang, Y. H. Percival Committee Chair
Barone, Justin Robert Committee Member
Renneckar, Scott H. Committee Member
Reynolds, William T. Jr. Committee Member
Keywords
  • biomass pretreatment
  • cellulose solvents
  • biofuels
  • enzymatic hydrolysis
Date of Defense 2011-08-22
Availability unrestricted
Abstract
The production of biofuels and biobased products from low-cost abundant renewable non-food lignocellulosic biomass will be vital to sustainable development because it will bring benefits to the environment, the economy, and the national security. The largest technical and economic challenge for emerging biorefineries is cost-effective release of fermentable sugars from recalcitrant structure of lignocellulosic biomass.

Cellulose- and organic-solvent-based lignocelluloses fractionation (COSLIF) technology was employed to overcome biomass recalcitrance. Surface response methodology (SRM) showed that optimal COSLIF pretreatment conditions were 85% (w/v) H3PO4 and ~50 oC, regardless of moisture contents in biomass from 5-15% (w/w) for common reed. Under these conditions, the pretreated biomass was hydrolyzed fast with high glucan digestibilities at low enzyme loadings (i.e., one FPU of cellulase per gram of glucan). Crystallinity index (CrI) measurements by X-ray diffraction (XRD) and cross polarization/magic angle spinning (CP/MAS) 13C nuclear magnetic resonance (NMR), and cellulose accessibility to cellulase (CAC) determinations of COSLIF-pretreated biomass confirmed that highly ordered hydrogen-bonding networks in cellulose fibers of biomass were disrupted through cellulose dissolution in a cellulose solvent. This disruption of hydrogen bonding networks among cellulose chains resulted in a drastic increase in CAC values. Fourier transform infrared (FTIR) analyses on COSLIF-pretreated biomass revealed conformational changes in specific hydrogen bonding among cellulose chains due to COSLIF.

While CrI is believed to be a key substrate characteristic that impacts enzymatic cellulose hydrolysis, studies in this thesis showed CrI values varied greatly depending on measurement techniques, calculation approaches, and sample preparation conditions. A correlation between CAC values and glucan digestibility of pretreated biomass showed that substrate accessibility is a key substrate characteristic impacting enzymatic cellulose hydrolysis.

In summary, COSLIF can effectively overcome biomass recalcitrance. The resulting pretreated biomass has high CAC values, resulting in fast hydrolysis rates and high enzymatic glucan digestibilities of COSLIF-pretreated biomass at low enzyme usage.

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