Monday, April 19, 2010: 4:00 PM
Salon F-G (Hilton Clearwater Beach)
Shishir Chundawat1, Albert Cheh
2, Leonardo Sousa
1, Nirmal Uppugundla
1, Dahai Gao
1, Paul Langan
3, S. Gnanakaran
4, Giovanni Bellesia
4, Umesh Agarwal
5, Chris Bianchetti
6, George Phillips Jr.
6, Venkatesh Balan
1 and Bruce Dale
1, (1)Chemical Engineering and Materials Science, Michigan State University, Lansing, MI, (2)Environmental Science and Chemistry, American University, Washington, DC, (3)Biosciences Division, Los Alamos National Laboratory, Los Alamos, NM, (4)Theoretical Biology and Biophysics Division, Los Alamos National Laboratory, Los Alamos, NM, (5)USDA-Forest Products Laboratory, Madison, WI, (6)Department of Biochemistry, University of Wisconsin-Madison, Madison, WI
Cellulose is known to exist in various polymorphic states (I, II, III) that vary in susceptibility to enzymatic hydrolysis. The effect of cellulose crystal structure on cellulase digestibility was explored using various cellulosic substrates (e.g. Avicel, linters, cotton, and corn stover). Native cellulose I was transformed to cellulose IIII and III by treatment with anhydrous liquid ammonia and sodium hydroxide, respectively. On the contrary, there was no formation of cellulose II or III upon treatment with ammonium hydroxide. The effect of ammonia pretreatment parameters (ammonia/water loading, residence time, temperature) on the extent of conversion of cellulose I to IIII was quantified by X-ray diffraction and Raman spectroscopy. The differential hydrolysis kinetics for cellulose depended on its crystalline form, which proceeded in the following order; Amorphous cellulose > Cellulose IIII > Cellulose II > Cellulose I. Interestingly, the enzymatic hydrolysis rate for cellulose IIII was found to be at least 2 folds greater than native cellulose I. Improvement in hydrolysis rate for cellulose III was found to be largely attributable to enhanced endoglucanase activity. Theoretical studies are being utilized to elucidate the differences in glucan chain packing (via modification of hydrogen bonding and hydrophobic interactions) for cellulose III versus native cellulose that may be responsible for the remarkable increase in the hydrolysis rate.
