P45: Statistical optimization of enzymatic hydrolysis of prairie cordgrass for enhanced bioethanol production

Response surface methodology (RSM) was used to optimize the enzymatic hydrolysis of prairie cordgrass (PCG), native to North America, to fermentable sugars. Prior to enzymatic hydrolysis, PCG was thermo-mechanically pretreated on a single screw extruder. The extruded PCG was then hydrolyzed with the crude cellulase of Penicillium pinophilum ATCC 200401 and then fermented to ethanol with Saccharomyces cerevisiae ATCC 24860. A three-level, three-variable central composite design (CCD) was employed in a total of 20 experiments to model and evaluate the impact of pH (4.1-6.0), solids loadings (6.6-23.4%), and enzyme loadings (6.6-23.4 FPU g^-1 DM) on cellulose hydrolysis of extruded PCG. All three variables had a significant impact on the glucan hydrolysis. Analysis of variance (ANOVA) showed a high coefficient of determination R² of 0.89. At the optimal conditions of pH of 4.5, solids loadings of 10%, and enzyme loadings of 20 FPU g^-1 DM, enzymatic hydrolysis of pretreated PCG hydrolyzed nearly 74% of the total glucan which resulted in ethanol yields in excess of 78% from the theoretical maximum. The predicted results based on the RSM regression model were in good agreement with the actual experimental values.