One-Pot High-Gravity Bioethanol Fermentation from Choline-Based Ionic Liquid Pretreated Corn Stover

One-pot high-solid biomass process for biofuel production is not available because of poor mass transfer, concentrated inhibitory products, and high osmolarity, etc. In this report, high gravity biomass processing, including ionic liquid pretreatment, enzymatic saccharification, and yeast fermentation, was developed and optimized for high-titer cellulosic ethanol production in one pot. The study improved the biomass digestibility at a solid loading over 30 % by investigating the interaction between ionic liquid loading and biomass loading. For the first time, over 40 g L^-1 of ethanol was obtained at an overall yield of 74.8% with the integrated one-pot system. The integrated fed-batch system that constitutes of seed batch and operation batches is able to continuously provide concentrated hydrolysates for simultaneous saccharification and fermentation. Benefiting the optimized one-pot design, the high-solid processing reduced the overall water usage to a remarkably low number, around 3 kg per kg biomass. The developed fed-batch simultaneous saccharification and fermentation could be enhanced for continuous fermentation with minimal modification.