Fig. 1

Glucose and xylose yields following enzymatic hydrolysis of alkaline pre-extracted (in water or ethanol) and fed-batch Cu-AHP pretreated hybrid poplar (yields based on composition of alkaline pre-extracted biomass). All pretreatment reactions were performed for 24 h at 10% (w/v) solids. For the two 120 °C pre-extractions completed as part of this study, particle size was 3–7 mm for pre-extraction and 1 mm for Cu-AHP pretreatment. The temperature for pretreatment was 30 °C, with final concentrations of 1 mM Cu²⁺ and 2 mM bpy, and a H₂O loading of 100 mg/g biomass. Enzyme loadings for enzymatic hydrolysis were 30 mg total protein per g glucan. The 30 °C pre-extraction was from a previous study [13]. Experimental conditions were largely the same as above, except that samples were milled to pass through a 20-mesh screen (0.85 mm) prior to pre-extraction, and enzyme loadings of 60 mg total protein per g glucan. The data points are the averages of three independent experiments, and the error bars represent ± standard deviations of the means