(731c) Understanding the Effects of Ammonia and Organosolv Pretreatments on Physicochemical Characteristics of Lignin

Pretreatment is an important step in biological conversion of biomass. It renders structural changes of biomass to reduce the biomass recalcitrance, thus enhancing its sugar release performance. Lignin is one of major barriers for lignocellulosic biomass utilization; therefore, various pretreatment methods have been studied to reduce the recalcitrance of biomass by removal and/or modification of lignin in the biomass. Among many pretreatment methods, two pretreatment methods using ammonium hydroxide and organic solvents were selected to understand how these methods reduces the recalcitrance and improves sugar release. In this study, the crude lignins isolated from poplar and switchgrass were subject to aqueous ammonia and organosolv pretreatments, and the effects of each pretreatment on lignin structural changes were investigated. Physicochemical characteristics of the lignins during the pretreatments were analyzed by diverse analysis methods. Chemical compositions of soluble fraction and residual solid fraction were analyzed by HPLC and GCMS. Molecular weights of both fractions were investigated using GPC. 2D ¹³C-¹H HSQC NMR and ³¹P NMR analyses were conducted to reveal the structural and chemical transformation of lignin. Adsorption of enzymes on the pretreated lignin was also investigated.