LAUSR

Supercritical carbon dioxide (SCCO2) was employed as pretreatment of blue agave bagasse (BAB) to enhance enzymatic hydrolysis (EH) to simple sugars in preparation for bioethanol fermentation. Processing time (10–120 min), temperature (24–120 °C), and pressure (80–350 bar) were evaluated to obtain maximum total reducing sugar (TRS) after EH with commercial cellulase. Effect of water activity (aw) (0.082–0.973) of BAB was evaluated after optimum pretreatment conditions for maximum TRS (100 °C, 280 bar, and 10 min) were established. Higher values of temperature or pressure degraded simple sugars as determined by relative furan analysis. Treated samples were also characterized by scanning electronic microscopy and porosimetry, showing structural and morphological modifications that enhance enzymatic digestibility as compared to untreated controls. Processing with SCCO2 results in 40% increment in TRS compared with untreated BAB. Hydration level defined by aw resulted in the main variable affecting sugar yields, with lowest aw of pretreated BAB generating the highest TRS valued. It is proposed that at low hydration levels, diffusivity of CO2 is greater facilitating infiltration into the matrix and a more extensive deconstruction of the tight lignocellulosic matrix by explosion when pressure is released.