Disc Milling of Fermented Corn Stover to Increase Its Accessibility to Fermentation By Clostridium Thermocellum

We are investigating mechanical disruption during fermentation (cotreatment) as an alternative to thermochemical pretreatment to increase the accessibility of lignocellulose to biological attack. To be feasible, cotreatment requires that three things be achieved simultaneously: high carbohydrate-to-sugar conversion (solubilization), active biocatalysts in the presence of milling, and low milling energy requirements. This talk presents results for two fermentation with disc milling configurations: in situ milling of fermenting biomass slurries and ex situ milling featuring sequential fermentation, milling, and fermentation. Cotreatment using in situ milling demonstrated that solubilization is increased, and that the microbial culture is able to withstand the milling process. Ferment-mill-ferment experiments were performed at low and high solids loadings and for the first time, energy consumption of milling partially fermented biomass was measured. The impact of solids loading was investigated, and carbohydrate solubilization and milling energy consumption were compared for two types of disc mills. Perspectives will be offered on progress and outstanding issues related to establishing the efficacy and industrial feasibility of the cotreatment approach.