Monday, April 29, 2013
Exhibit Hall
Cellulosic biomass recalcitrance to biological conversion is multifold in that it is believed that cellulose accessibility to cellulase is one of major factors controlling cellulose hydrolysis rates and yields. Accessibility, in turn, is believed to be affected by several substrate features such as lignin and hemicellulose contents and their location in plant cell wall, cellulose crystallinity, pore volume, surface area, and reducing ends. However, in this study, in line with our previous hypothesis that cellulose accessibility and enzyme effectiveness once adsorbed onto biomass are the two main factors 1, 2controlling effective enzymatic hydrolysis, it was found that cellulose recalcitrance, without much change in crystallinity, chain length (reducing ends), and accessibility, was significantly enhanced (>50% drop in hydrolysis relative to control) by the regioselective oxidation of other cellulose hydroxyl groups than those in position 1(C-1; reducing ends) while cellulose reducing ends play a lesser role in cellulose recalcitrance. The enzymatic hydrolysis performed at low to high cellulase protein loadings showed that to achieve similar conversions as control, oxidized cellulose required almost 10-12 times more cellulase protein than control. Furthermore, multifaceted characterizations were performed to unravel the structural changes that resulted in such enhanced recalcitrance.
1. R. Kumar, G. Mago, V. Balan and C. E. Wyman, Bioresour. Technol., 2009, 100, 3948-3962.
2. R. Kumar and C. E. Wyman, in Bioalcohol production : Biochemical conversion of lignocellulosic biomass, ed. K. Waldon, Woodhead publishing limited, Oxford, 2010, pp. 73-121, invited.
*rkumar@cert.ucr.edu