Investigation of various pretreatments on recalcitrance of natural poplar variants

The natural recalcitrance of biomass is a critical issue for the viable biomass to biofuel process that is considered to be largely due to the complex physical/chemical structures of plant cell walls. Natural Populus Trichocarpa variants and a baseline poplar were selected to subject to various pretreatment processes including dilute acid, hot water, alkaline and organosolv pretreatment. The pretreated poplar variants were enzymatically hydrolyzed and their respective sugar release performance on various pretreatment was investigated. The results showed that organosolv pretreatment resulted in the highest sugar release over among all the samples (~92% for variant #328), followed by dilute acid pretreatment (~76%); while the hot water and alkaline pretreatment had comparable glucose yield (~60%). Compared to the baseline poplar, the natural poplar variants showed higher glucose yield by 5-21% after all the four types of pretreatment indicating a lower recalcitrance of natural variants. In addition, the structural features resulted from various pretreatment were investigated using FTIR, NMR and GPC techniques, in an effort to better understand the contributions of physical/chemical features on biomass recalcitrance and sugar release performance.