Effect of Extruder Parameters and Moisture Content of Corn Stover and Big Bluestem on Sugar Recovery from Enzymatic Hydrolysis

Abstract

Biomass pretreatment has been in place for more than three decades. Extrusion can be a viable continuous pretreatment method due to its processing mechanisms compared to other conventional methods. Extruder screw compression ratio, screw speed, and barrel temperature are the important factors that can influence sugar recovery from biomass; however, no comprehensive study has been reported for corn stover and big bluestem. Hence, the current study was undertaken to select a screw compression ratio for maximum sugar recovery, to investigate the effect of extruder screw speed and barrel temperature on sugar recovery, and to understand the influence of moisture content of corn stover and big bluestem on sugar recovery. Ground, moisture balanced (15%, 25%, 35%, and 45% w.b.) corn stover and big bluestem was pretreated at various barrel temperatures (50°C, 100°C, and 150°C), and screw speeds (50, 100, and 150 rpm) using two different screw compression ratios (2:1 and 3:1). Statistical analyses revealed that not only the independent variables but also their interactions had a significant effect on sugar recovery from both biomasses. A combined sugar recovery of 90% was achieved when corn stover was pretreated at a screw speed of 150 rpm, a barrel temperature of 150°C, and a moisture content of 15% when used with a 3:1 compression ratio. This pretreatment condition produced 0.24 g acetic acid L-1 of hydrolyzate. For big bluestem, maximum glucose (55.2%), xylose (92.8%), and combined sugar recovery (65.4%) was obtained at a screw speed of 100 rpm, a barrel temperature of 150°C, 15% moisture content, and a 3:1 compression ratio.