Date of Award

3-2010

Degree Type

Thesis

Degree Name

Master of Science

Major

Forestry

Major Professor

David Harper

Committee Members

Siqun Wang, David Joy

Abstract

Plant cell walls compose the largest source of sugars on earth and are a potential source after conversion for liquid transportation fuels. However, the crystalline region of cellulose and the lignin that incases it present significant obstacles for enzymes to digest. This lowers the sugar yield, which ultimately decreases the production efficiency of bioethanol. A pretreatment that could help lowering the amount of crystallinity; meanwhile, breakdown the matrix of lignin and polysaccharides that cover cellulose fibers would be ideal. Here we propose a physical pretreatment strategy of electron beam irradiation that could potentially decrease cellulose crystallinity as well as unzip the lignin structure. Four types of biomass: cellulose, yellow pine, yellow poplar, and switchgrass were irradiated with a 12 MeV electron beam (Sterigenics, Inc.) at dosages of 0, 54, 80, 148 and 403 kGy. By combining the result from the wet chemical analysis of percent weight glucose/ cellulose from the HPLC, percent crystallinity from the Wide Angle X-Ray Diffraction (WAX) and the change of chemical functionality from Fourier Transform Infrared Spectrometer (FTIR), a promising effect is obtained in pine and yellow poplar but not in cellulose and switchgrass. A significant increase in percent glucose is observed for pine at higher doses as shown by (r = 0.97, P< 0.0076) which are 9.4 and 27% at 0 and 403 kGy. The amount of glucose considerably changes from all different types of biomass over time (P< 0.0001). A strong correlation of decreasing in percent crystallinity was found in poplar (r = -0.89, P< 0.05) from 32.4% to 17.4% and related to an average increase in percent glucose produced from 30 to 55% comparing between 0 and 403 kGy.

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