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Vacuum-coupled High-Solid Fermentation of Corn for Bioethanol Production
D. KUMAR (1), V. Singh (1) (1) University of Illinois at Urbana-Champaign, Urbana, IL, U.S.A..

Bioethanol, an important renewable transportation fuel, can be produced in significant quantities from fermentation of sugars obtained from starch or cellulose. The solid loading during the simultaneous saccharification and fermentation (SSF) process directly affects the final ethanol concentrations. High ethanol concentrations in the fermentation beer can significantly reduce the energy requirements for subsequent ethanol recovery and improve the plant productivity. However, during ethanol production from corn, the solid loadings during the fermentation process are restricted to 32% w/w due to inhibition by high ethanol concentrations. Simultaneous stripping off of ethanol under vacuum during SSF process is one of the potential approaches to reduce this inhibition. The objective of this study is to investigate the feasibility of this vacuum-coupled SSF strategy for high solid SSF of corn. The approach was tested for 40% solid loading using the dry grind ethanol process. Various vacuum cycles (time for one stripping) and interval periods were investigated to identify the conditions for maximum ethanol yields. Application of vacuum for 1h at 12, 24, 36 and 48h during SSF process resulted in complete fermentation compared to 13.6% residual sugars in case of conventional process. The final ethanol yield was estimated as 0.414 L per kilogram dry corn, which was about 1.68 times that for conventional fermentation. To determine the commercial scale feasibility of the process, a detailed techno-economic analysis will be performed by developing a comprehensive process model for the dry grind ethanol with vacuum stripping system. The model will also help in identifying the optimum vacuum stripping conditions for maximum ethanol yields with least energy consumption