Pressurized liquid hot water pretreatment and enzymatic hydrolysis of switchgrass aiming at the enhancement of fermentable sugars

Abstract

Pressurized Liquid Hot Water (PLHW) process is an essential and new method to remove lignin from biomass for biorefinery applications. In this study, a cascade method was investigated to obtain reducing sugars of switchgrass using optimization of PLHW and enzymatic hydrolysis. Optimization of pressurized liquid hot water and enzymatic hydrolyses were achieved by Box-Behnken design. First, pretreatments including PLHW were carried out step by step, with respect to the independent variables such as temperature (100, 140, 180 °C), pressure (100, 150, 200 bar) and time (20, 40, 60 min) at fixed flow rate (2 ml/min). The conditions which give the most optimized reducing sugar were 122.12 °C, 100 bar and 50.08 min and optimized fermentable sugar content was measured 107.49 g/l. Then, enzymatic hydrolysis was applied to solid phase with 4.8 pH citrate buffer at 50 °C during 24, 48 and 72 h with the help of Novozyme 188 and Celluclast enzymes. The reducing sugar amount obtained from switchgrass with enzymatic hydrolysis was measured 248.23 g/L, which means totally 355.72 g/L.