Ethanol Production from High-Solid SSCF of Alkaline-Pretreated Corncob Using Recombinant Zymomonas mobilis CP4

In this work, Zymomonas mobilis was genetically improved for pentose utilization to increase the final ethanol concentration. It showed good fermentation ability on both soluble sugar mixture and lignocellulose. Nearly all the glucose and xylose in sugar mixture can be consumed, corresponding to 86 % of theoretic ethanol yield. Simultaneous saccharification and co-fermentation (SSCF) of NaOH-pretreated corncob was then carried out in a high dry matter (DM) loading of 15–25?w/v%. At the DM loading of 15 %, the suitable operating conditions were determined, i.e., Z. mobilis loading of 0.30 g dry weight/L at 30 °C (pH?5.5), under which the ethanol concentration reached 49.2 g/L. Higher final ethanol concentrations were obtained when SSCF was operated at the fed-batch mode. Several amounts of substrate (1 % to 10 %) were added, and the highest final ethanol concentration (60.5 g/L) was obtained at 10 % DM addition.