Monday, April 30, 2007

The effect of different drying regimes on the enzymatic hydrolyzability of pretreated lignocellulosics

Pablo Chung, Alex Berlin, Michael Liu, and Jack Saddler. Forest Products Biotechnology, Wood Science, The University of British Columbia, 4609-2424 Main Mall, Vancouver, BC V6T1Z4, Canada

A sustainable production of cellulosic ethanol will be possible if a diverse and abundant supply of lignocellulosic biomass will become available at low cost. Lignocellulosic biomass for ethanol production will therefore necessarily include a large diversity of agricultural and forest residues, purpose-grown crops, and municipal wastes. This expected variety will result in significant variability of biomass chemical and physical properties. The influence of these variables on the enzymatic hydrolyzability of cellulose and hemicellulose in lignocellulosics is currently under study in our group.

Biomass conditioning for bioconversion is a necessary step before starting the enzymatic degradation of the substrate. This stage generally includes screening of impurities, size reduction, and moisture content adjustment. Moisture content is considered an important chemical property that has extensive influence on the substrate physical properties. The overall accessibility of biomass-degrading enzymes to the substrate can be affected by modifying the moisture content in biomass. In spite of the significance of this property the information available in the literature on the hydrolyzability of pretreated lignocellulosic substrates differing in moisture content remains ambiguous. Moisture content reduction by drying or pressing is frequently included in a bioconversion process to maximize the solids concentration in the final reaction mixture or to minimize the possibility of microbial contamination. This study describes the effect of different drying regimes on the enzymatic hydrolyzability of a steam-exploded rice straw and an organosolv-pretreated hybrid spruce pretreated at low, mild, and high severity.