Alkaline twin-screw extrusion fractionation of olive-tree pruning biomass

The present study investigates and optimizes a one-step alkaline-extrusion pretreatment process using olive tree pruning as feedstock. In this work, a range of pretreatment conditions (temperature, screw speed and alkaline catalyst to dry matter ratio) were evaluated according to different parameters: composition of pretreated substrates, glucose and xylose recovery, degradation products generation, enzymatic hydrolysis yield and overall sugars yield. Results show that enzymatic digestibility is remarkably improved by extrusion although not significant variations are found on the chemical compositions of extruded material produced at different conditions. The maximum glucose sugar production value, after pretreatment and enzymatic hydrolysis, was close to 21 g/100 g raw material, which corresponds to about 69% of the theoretical production yield.