Integration of corn ethanol and corn stover ethanol processes for improving xylose fermentation performance

Xylose fermentation is an essential issue for lignocellulosic ethanol production, which is often inhibited by degradation products generated during biomass pretreatment. In this study, enzymatic hydrolysate of dilute acid pretreated corn stover was fermented using Zymomonas mobilis 8b. With the solid loading of corn stover increased from 5 to 24 wt.%, the xylose consumption volume decreased from 97.0 to 21.5%. The ethanol produced ranged from 7.8 to 28.6 g/L. In order to improve xylose consumption, corn slurry was integrated into the corn stover ethanol process. Integration strategies, glucoamylase dosage, and corn–corn stover mixing ratio were investigated. Results showed that introducing corn slurry into corn stover hydrolysate was an effective way to improve xylose fermentation as well as enhance ethanol titer. Specifically, when liquefied corn slurry was introduced into corn stover hydrolysate at the ratio of 1:1 and total solid loading of 24%, the xylose consumption volume exceeded 88% with the final ethanol titer reached 68.6 g/L. This study indicates that integration of the first- and the second-generation ethanol processes is beneficial to xylose fermentation.