Switchgrass and coastal bermudagrass were pretreated by ammonia fiber explosion (AFEX), and the treated materials hydrolyzed using 5 IU cellulase/g substrate. Resulting sugar solutions (2-3%, w/v) were fermented with recombinant Klebsiella oxytoca. Glucose was rapidly and completely fermented to ethanol, whereas xylose fermentation was slower and less complete. At higher sugar concentrations (similar to 8%) glucose fermentation continued, but xylose fermentation almost ceased. Protein extraction somewhat enhanced ethanol production from coastal bermudagrass. Improved fermentation technologies and media appear necessary for practical mixed-sugar lignocellulosic hydrolyzates.