Effect of solids loading on Saccharomyces cerevisiae strain XR122N. (A) Freeze-dried XR122N was inoculated at an initial concentration of 4 g/L cell dry weight (dcw) into small-scale bioreactors containing pretreated pine at a solids loading of 5% (green diamonds), 10% (blue circles), and 12% (red triangles) w/v. Cellulases and cellobiase were added simultaneously with the inoculum (15 FPU cellulase, and 60 CU cellobiase per gdw of pretreated pine). (B) XR122N was inoculated into 12% w/v solids loading of pretreated pine in a freeze-dried state at an initial concentration of 4 g/L dcw (black squares), 2.0 g/L dcw (red diamonds), 1.0 g/L dcw (blue circles), or 0.5 g/L dcw (green diamonds). Fermentations were maintained at 35°C, pH 5.0, and performed in triplicate. Error bars represent one standard deviation from the mean. FPU, filter paper units; dcw, cell dry weight; gdw, gram dry weight; CU, cellobiase units.