Xinglian Geng1, Brandon Jones2, and Wesley A. Henderson1. (1) Chemical and Biomolecular Engineering, North Carolina State University, 911 Partners Way, Raleigh, NC 27695, (2) Wood and Paper Science, North Carolina State University, 2105 Biltmore Hall, Raleigh, NC 27695
Pretreatment of biomass using both alkali extraction and ionic liquid (IL) dissolution is found to be highly effective for enzymatic hydrolysis. Intensive efforts have been devoted to exploring the enzymatic hydrolysis of lignocellulosic biomass to fermentable sugars for fuel production. The hydrolysis efficiency of a given lignocellulosic biomass is the result of the complex interplay of various factors including both enzyme and substrate properties. Substrate properties are governed by the biomass identity and pretreatment process employed. By controlling the type and conditions of the pretreatment process, the substrate-related factors that govern enzymatic hydrolysis can be modified appreciably. Neither acidic nor alkali pretreatments change the cellulose crystalline structure, but IL dissolution does. ILs are salts, which melt at low temperature. These liquid salts can dissolve cellulose and, once regenerated after dissolution, the cellulose structure can be altered from highly crystalline to amorphous, and the degree of polymerization may be reduced. Our research indicates that lignin is a barrier to the IL dissolution and enzymatic hydrolysis. Alkali extraction has therefore been used prior to IL dissolution of the cellulose. In addition to changing the chemical composition of the substrate by reducing the lignin content, alkali solutions cause strong intracrystalline swelling of cellulose further facilitating dissolution by the IL. By adjusting the time, temperature, alkali (NaOH) concentration and solid/liquid ratio during alkali extraction of corn stover, substrates with varied lignin and hemicellulose contents and fiber surface area were collected. The relationship between the substrate properties and enzymatic hydrolysis efficiency have been quantitatively analyzed.
