Enzymatic hydrolyses of pretreated eucalyptus residues, wheat straw or olive tree pruning, and their mixtures towards flexible sugar-based biorefineries

Eucalyptus residues, wheat straw, and olive tree pruning are lignocellulosic materials largely available in Southern Europe and have high potential to be used solely or in mixtures in sugar-based biorefineries for the production of biofuels and other bio-based products. Enzymatic hydrolysis of cellulose is commonly used in this context, but its high efficiency is mandatory for cost-competitive biorefineries. The influence of pretreatment severity (hydrothermal at 210–230 °C), enzyme dosage (8–24 FPU/g_solids), and solid loading (5–20 % w/v) as key factors on enzymatic hydrolysis efficiency was studied by 2³ complete factorial central composite design followed by response surface methodology analysis, towards the optimization of glucose recovery from individual feedstock or their mixtures. Optimized conditions for enzymatic hydrolysis at 20 % (w/v) solids reached glucose recoveries between 80 and 110 g/L for individual feedstock and 85–92 g/L for mixtures and yields over 80 %.