A residue-free and effective corncob extrusion pretreatment for the enhancement of high solids loading enzymatic hydrolysis to produce sugars

Abstract

To convert biomass into biofuel, pretreatment is the first stage required to de-structure lignocellulose – twin-screw extrusion is one of the viable pretreatment technologies. The enzymatic hydrolysis of corncobs pretreated with twin-screw extrusion to obtain sugar was evaluated. Corncob extrusion (115–130 °C; 14 rpm) was enhanced through the employment of additives (water and glycerol, 25:25, % w/w). By reproducing the response surface methodology (RSM) technique, the maximized glucose productivity (0.69 g L −1 h −1 ) and conversion of cellulose to glucose (90.4 % w/w), as well as hemicellulose to xylose and arabinose (44.0 % w/w) were established with the dosage of the commercial enzymatic complex Cellic Ctec2 (32 FPU/g dry lignocellulosic material ) and solids loading (17.8 % w/w). Total sugar yield was of 471 kg (glucose 323 kg; xylose and arabinose 148 kg) for a dried corncob ton. Kinetic constants of the Michaelis-Menten model, V max and K m , for converting cellulose to glucose were of 6.00 % (w/w)/h and 22.59 g cellulose /L solution , respectively. A residue-free and effective corncob extrusion pretreatment enhanced high solids loading enzymatic hydrolysis to achieve a glucose-rich solution. • Corncob clean extrusion pretreatment favored enzymatic hydrolysis for sugar release. • Corncob extrusion was optimized using additives (water and glycerol, 25:25, % w/w). • Glycerol as a corncob extrusion additive did not interfere in the enzymatic hydrolysis • Higher extruded corncob loading favored high cellulose-to-glucose conversion (> 90 %). • Kinetic study showed 40.6 %-time improvement for extruded corncob enzymatic hydrolysis.