Biomass from agricultural/forestry waste and energy crop plantations is available in large quantities for the production of renewable fuels and chemicals. Utilization of biomass delivers many ecological and agronomical benefits, and supports the growth of a sustainable economy. The cell wall polysaccharides in biomass can be enzymatically hydrolyzed to monomeric sugars, which in turn can be used as an intermediate platform chemical for the production of biofuels and biochemicals via catalytic transformation and microbial fermentation processes. A major challenge faced by many biomass conversion strategies is the low enzymatic digestibility of cell wall polysaccharides, which is caused by the plants' natural defense against enzymatic attack and deconstruction. To impair this defense and to prepare biomass for efficient enzymatic conversion, many pretreatment technologies have been designed and employed.Michigan State UniversityWe have developed a novel catalytic oxidative pretreatment technology, a.k.a. the Cu(bpy)-AHP pretreatment. The enzymatic hydrolysis yields of sugars from woody biomass (e.g. hybrid poplar) can be improved by two to three folds as the result of the Cu-catalyzed hydrogen peroxide oxidation during Cu(bpy)-AHP pretreatment. Under particular reaction conditions, we achieved high efficacy of pretreatment in about 1 hour of pretreatment with modest consumption of chemicals. Through tuning of operation variables and improvements in process integration, a scheme for bio-ethanol production from Cu(bpy)-AHP pretreated hybrid poplar has been established for techno-economic evaluation and further development.Detailed characterization of Cu(bpy)-AHP pretreated biomass with heteronuclei NMR spectroscopy and TEM microscopy reveals oxidative modifications of lignin as the result of the pretreatment, as well as disruption of lignified cell wall structure. As the result of modest oxidation and depolymerization reactions, a significant proportion of lignin in the plant cell wall is solubilized during Cu(bpy)-AHP pretreatment. Microscopic and spectroscopic analyses highlight the role of metal-catalyzed oxidation reactions in close vicinity of the biomass surface. Analysis of biomass degradation products released during pretreatment suggests that Cu-catalyzed oxidation is a viable technology as both a biomass pretreatment and a process for sustainable production of aromatic chemicals such as vanillin.
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