(602p) Comparison of Enzymatic Reactivity of Corn Stover Solids Prepared by Dilute Acid, AFEX, and Ionic Liquid Pretreatments

This study is part of a collaboration among the BioEnergy Science Center (BESC), the Great Lakes Biomass Research Center (GLBRC), and the Joint Biological Energy Institute (JBEI), the goal of which is to understand how biomass pretreatments with much different deconstruction patterns impact the chemical and structural features of biomass and its biological conversion to sugars.

 Enzymatic hydrolysis was performed on solids resulting from dilute sulfuric acid (DA), ammonia fiber expansion (AFEX), and ionic liquid (IL) pretreatments of corn stover at low to high protein loadings to define how ratios of cellulase, xylanase, and pectinase affected sugar yields.  Avicel cellulose, regenerated amorphous cellulose (RAC), and beechwood xylan were also subjected to enzymatic hydrolysis. Initial hydrolysis rates, sugar release patterns over 120 h of hydrolysis, cellulase accessibility to cellulose, and oligomers concentrations were measured over the course of enzymatic hydrolysis to determine enzyme-substrate interactions. These results were then integrated with compositional changes to identify key features controlling enzymatic hydrolysis of solids from these pretreatments and similarities and differences in their impacts on enzyme effectiveness. Ionic liquid pretreated corn stover displayed the highest initial reactivity at all enzyme loadings and the highest final digestibility for a low enzyme loading of 3 mg protein/g glucan in the raw material. However, increasing the enzyme loading to 12 mg/g glucan resulted in dilute acid and AFEX pretreated corn stover attaining the highest overall cellulose digestions.  Hydrolyzate from AFEX pretreated corn stover had the highest proportion of xylooligomers, while ionic liquid pretreated produced the most glucooligomers, but amounts of both oligomers dropped with increasing enzyme loadings and hydrolysis times.  Ionic liquid pretreated corn stover had the greatest accessibility to enzymes as measured by the maximum cellulase adsorption capacity.