Efficient processes for converting lignocellulosic hydrolysates to ethanol require optimal utilization of the biomass-derived sugars present in these materials.  This study evaluated fermentation performance of the glucose-xylose fermenting recombinant Zymomonas mobilis strain 8b using various process configurations. The goal was to determine the microorganism’s ability to produce high ethanol concentrations and yields at high hydrolysate solids loadings. Dilute acid pretreated corn stover slurries were produced in a pilot scale pretreatment reactor and the whole slurry or liquor fraction was subsequently conditioned by ammonium hydroxide.  When processing whole slurries, a simultaneous saccharification and fermentation process (SSF) or a separate hydrolysis and fermentation (SHF) process was tested. The liquor fraction was also removed from the solids and conditioned, and then fermented at various dilutions to assess the microorganism’s tolerance to high concentrations of inhibitors. A whole slurry SHF at a 20% (w/w) total solids concentration achieved an ethanol yield of 55% and used 40% of the available xylose, while an SSF using this microorganism performed poorly.  However, fermentation of the separated liquor fraction at the same equivalent strength achieved an 89% ethanol yield and used 95% of the available xylose.  At a higher liquor strength equivalent to whole slurry at 25% total solids, the ethanol yield dropped to 75% and 82% of the available xylose was used. This study showed that better ethanol yields can be achieved in the liquor only fraction, but further exploration is necessary to explain this behavior.