(519b) Mechanistic Modeling of the Enzymatic Saccharification of Cellulose-Iβ and Cellulose-III: Parameter Determination and Model Validation

Cost-effective production of fuels and chemicals from lignocellulosic biomass often involves enzymatic saccharification, which has been the subject of intense research and development. Recently, a mechanistic model for the enzymatic saccharification of cellulose has been developed that accounts for distribution of cellulose-chain lengths, the accessibility of insoluble cellulose to enzymes, and the distinct modes of action of the component cellulases [Griggs et al. (2012) Biotechnol. Bioeng., 109(3):665–675; Griggs et al. (2012) Biotechnol. Bioeng., 109(3):676–685]. However, determining the appropriate values for enzyme adsorption, inhibition, and rate parameters required further experimental investigation. In this work, we performed several sets of experiments to aid in parameter estimation and to quantitatively validate the model.  Several cellulosic materials having varied degrees of polymerization, crystallinity, and crystalline allomorph (cellulose-I_β and cellulose-III_I) were digested by component enzymes (EGI and CBHI) and by cocktails of these enzymes.  Based on information from the literature and the results from these experiments, a single set of model parameters was determined and used to produce model simulation results.  The agreement between simulation results and experimental data will be demonstrated.  Cases of discrepancy point the way for further model development.