Influence of Extruder Temperature and Screw Speed on Pretreatment of Corn Stover while Varying Enzymes and Their Ratios

Abstract

Pretreatment is being the first and most expensive step, it has pervasive impacts on all other steps in overall conversion process. There are several pretreatment methods using physical, chemical, and biological principles which are under various stages of investigation. Extrusion can be used as one of the physical pretreatment methods towards biofuel production. The objective of this study was to evaluate the effect of barrel temperature and screw speed on sugar recovery from corn stover, to select a suitable enzyme combination and its ratio. Corn stover was pretreated in a single screw extruder with five screw speeds (25, 50, 75, 100, and 125 rpm) and five barrel temperatures (25, 50, 75, 100, and 125 degrees C). In order to select a suitable enzyme combination and ratio, different levels of cellulase and beta-glucosidase, multienzyme complex and beta-glucosidase were used during saccharification of pretreated corn stover. From the statistical analysis, it was found that screw speed and temperature had a significant effect on sugar recovery from corn stover. Higher glucose, xylose, and combined sugar recovery of 75, 49, and 61%, respectively, were recorded at 75 rpm and 125 degrees C. This pretreatment condition resulted in 2.0, 1.7, and 2.0 times higher than the control sample using 1:4 cellulase and beta-glucosidase combination.

Effect of Extrusion Pretreatment on Enzymatic Hydrolysis of Miscanthus for the Purpose of Ethanol Production

“…7, No. 11;2015 significantly depended upon 8 model terms, that is particle size (p = 0.0003), barrel temperature (p < 0.0001), interactions between particle size and moisture content (p = 0.0107), moisture content and screw speed (p < 0.0001), and between barrel temperature and screw speed (p < 0.0001), and all quadratic terms but moisture content (p < 0.01). Coefficient of determination, R2 was determined to be 90.46% (p < 0.0001), which suggested that the model was suitable to adequately represent relationship among the selected independent variables, and was in agreement with the reported data for big bluestem (Karunanithy & Mutukumarappan, 2011a).…”

“…7, No. 11;2015 (a) (b) Figure 2. Response surface of xylose formation as a function of (a) moisture content and particle size (barrel temperature = 150 °C; screw speed = 2.5 Hz); (b) barrel temperature and particle size (moisture content = 15%; screw speed = 2.5 Hz)…”

“…7, No. 11;2015 four-factorial design with five replicates at the center points leading to 29 samples was employed for the optimization of the pretreatment processing conditions. Sample particle size (X 1 ) and moisture content (X 2 ), and barrel temperature (X 3 ) and screw speed (X 4 ) of the extruder were chosen for the independent variables and are shown in Table 1.…”

“…Sample particle size (X 1 ) and moisture content (X 2 ), and barrel temperature (X 3 ) and screw speed (X 4 ) of the extruder were chosen for the independent variables and are shown in Table 1. The levels chosen for each variable in this study were based on previous research (Xu, Wang, Jiang, Yang, & Ji, 2007;Karunanithy & Muthukumarappan, 2010); the dependent responses observed were glucose and xylose yields. Note.…”

“…These methods often involve high temperature which may lead to the formation of degradation products which act as inhibitors during fermentations (Olsson & Hahn-Hagerdal, 1996). Extrusion is a possible physical pretreatment alternative method, which can be used in the process of ethanol production (Karunanithy & Muthukumarappan, 2010;Liu et al, 2013).…”