Response Surface Methodology for Optimization of Corn Stover Pretreatment Using an Extruder

Abstract

Pretreatment is necessary to open up the biomass structure for increasing access of the hydrolytic enzymes. Extrusion might be a viable continuous pretreatment due to its advantages over other pretreatment methods. The current study was undertaken to investigate sugar recovery influenced by extruder factors such as barrel temperature (45°C to 225°C) and screw speed (20 to 200 rpm) and corn stover factors such as moisture content (10% to 50%) and particle size (2 to 10 mm), to optimize the above factors for maximum sugar recovery, and to propose mathematical models for predicting sugar recoveries from corn stover. Statistical analyses confirmed that all the independent factors studied had a significant effect on sugar recoveries. The quadratic polynomial model proposed to predict glucose, xylose, and combined sugar recovery had high F and R2 values along with low p-value, indicating that the model has the ability to represent the real relationship between independent factors studied. The optimum pretreatment conditions of 180°C barrel temperature, 155 rpm screw speed, 20% w.b. moisture content, and 8 mm particle size resulted in a maximum glucose, xylose, and combined sugar recovery of 85.7%, 87.5%, and 86.3%, respectively. The surface area of the optimally pretreated corn stover almost doubled compared to that of the control sample, which is the main cause for the increase in sugar recovery.