(116b) Kinetic Modelling of Lignocellulose Hydrolysis at High Solids Loading

Biomass slurries, required to achieve relevant sugar concentrations for biofuel/bioproduct manufacture must approach 200 g/L or higher. As higher concentrations are achieved, the biomass slurries become shear thinning. Consequently, the manner in which lignocellulose is added to the reactor, mixing conditions, and sequence of enzyme addition combine to exert a major influence on formation of a “flowing” biomass suspension, and the rates and extents to which the cellulose is hydrolyzed. We report work for corn stover. Our preliminary data show that, in a mixed reactor, conversion at constant enzyme loading may remain constant as solids concentrations increase from 10 to 200 g/L. At low loadings and minimal mixing, mass transfer through free water is readily achieved, while at high solids shear stress interferes with the productivity of the reactor, since higher viscosity may also inhibit rates of hydrolysis. Mixing decreases apparent viscosity and increases mass transfer resulting in a constant conversion at high loadings. This work relates viscosity to conversion and proposes an approach to predict liquefaction and cellulose hydrolysis as a function of shear stress, mixing, and enzyme addition strategies.