Switchgrass (Panicum virgatum) was subjected to hydrothermolysis pretreatment and then used to study the effect of enzyme loading and temperature in a simultaneous saccharification and fermentation (SSF) with the thermotolerant yeast strain Kluyveromyces marxianus IMB3 at 8% solid loading. Various loadings of Accellerase 1500 between 0.1 and 1.1 mL g-1 glucan were tested in SSF at 45 C (activity of enzyme was 82.2 FPU mL-1). The optimum enzyme loading was 0.7 mL g-1 glucan based on the six different enzyme loadings tested. SSFs were performed at 37, 41 and 45 C with an enzyme loading of 0.7 mL g-1 glucan. The highest ethanol concentration of 22.5 g L-1 was obtained after 168 h with SSF at 45C, which was equivalent to 86% yield. Four different batch and fed-batch strategies were evaluated using a total solid loading of 12% (dry basis). About 32 g L-1 ethanol was produced with the four strategies, which was equivalent to 82% yield.