Effect of Extruder Parameters and Moisture Content of Switchgrass, Prairie Cord Grass on Sugar Recovery from Enzymatic Hydrolysis

Abstract

Research on biomass pretreatment to enhance enzymatic digestibility has been done for more than decades, but a viable continuous pretreatment method needs to be developed. Extrusion has the potential to be a viable continuous pretreatment method. This study investigated the effect of compression ratio (2:1 and 3:1), screw speed (50, 100, and 150 rpm), and barrel temperature (50, 100, and 150 degrees C) on the sugar recovery from switchgrass (SG) and prairie cord grass (PCG) over a range of moisture contents (15, 25, 35, and 45% wb).The pretreated samples were subjected to enzymatic hydrolysis for sugar recovery measurement. Statistical analyses revealed that a 3:1 screw compression ratio (compared to 2:1) increased glucose recovery by 12% and 8% and combined sugar recovery by 37% and 40% for SG and PCG, respectively. For SG, the highest sugar recovery (45.2%) was obtained at the lowest screw speed (50 rpm) and the highest temperature (150 degrees C) with moisture content of 15%. The highest glucose, xylose, and combined sugar recovery of 61.4%, 84.3%, and 65.8% were recorded for PCG extruded at a screw speed of 50 rpm and a temperature of 50 degrees C with a moisture content of 25%. Glycerol and acetic acid were byproducts found in low concentration (0.02-0.18 g/L) for both biomass.