Monday, April 30, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
A major concern in lignocellulose conversion into fuels and chemicals is overcoming biomass recalcitrance through pretreatment while still maintaining green and energy efficient processing. Ionic liquids (ILs) are promising solvents for the pretreatment of lignocellulose as they are thermally stable, non-toxic, environmentally friendly, recyclable, and have low volatility. This study evaluated the effect of 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) for the pretreatment of energy cane bagasse in terms of biomass composition, structural changes, enzymatic digestibility, and ethanol yield. Energy cane bagasse was pretreated with 5% w/w [EMIM]OAc at 120 °C for 30 min followed by hydrolysis with commercially available enzymes, Spezyme CP and Novozyme 188. Saccharomyces cerevisiae D5A was added post hydrolysis for the conversion of glucose to ethanol. Changes in biomass structure were investigated by SEM, FTIR and X-ray powder diffraction (XRD). IL pretreatment removed 32.0% lignin and retained 91.2% glucan and 86.0% xylan. IL-treated biomass exhibited significantly higher cellulose and hemicellulose digestibility and ethanol yield (87.0%, 64.3% and 24.5 g/100 g dry biomass, respectively) than untreated (5.5%, 2.8% and 4.7g/100g dry biomass, respectively) and water-treated (4.0%, 2.1% and 5.0g/100g dry biomass, respectively) biomass. SEM images revealed a loose and disordered structure of biomass post pretreatment. FTIR analysis indicated that IL-treated biomass exhibited a significant loss of native cellulose crystalline structure. XRD analysis also confirmed that IL pretreatment resulted in a decrease of crystallinity index from 0.5628 to 0.2452. The enhanced digestibility of IL-treated biomass could be attributed to delignification and reduction of cellulose crystallinity.