7-03: Cell Wall Hydrophilicity Impacts on Enzymatic Digestibility for Alkaline Hydrogen Peroxide Pretreated Grasses

Treatment of biomass with alkaline hydrogen peroxide (AHP) can be used as a chemical pretreatment or alternatively as a post-treatment. This work will present research results of AHP pretreatment used as a post-treatment for liquid hot water (LHW) pretreatment as a delignifying step.  The effect of AHP on the carbohydrate and lignin compositional changes after pretreatment and fiber swelling behavior of corn stover and switchgrass will be shown as a function of hydrogen peroxide loading as well as the formation of potential fermentation inhibitors.  We hypothesize that the digestibility improvement resulting from AHP pretreatment may be attributed to mild oxidation or solubilization of the lignin remaining in the cell wall and, for grasses, destruction of ferulate crosslinks between cell wall polymers which would have the net effect of increasing the hydrophilicity to allow improved water and enzyme penetration into the cell wall.  To test this hypothesis, we will correlate the hydrophilicity of the cell wall as measured indirectly by lignin and cell wall carboxylic acid content to water swelling capacity, water activity at limiting free water, and digestibility.