Feasibility of Hydrothermal Pretreatment on Maize Silage for Bioethanol Production

The potential of maize silage as a feedstock to produce bioethanol was evaluated in the present study. The hydrothermal pretreatment with five different pretreatment severity factors (PSF) was employed to pretreat the maize silage and compared in terms of sugar recovery, toxic test, and ethanol production by prehydrolysis and simultaneous saccharification and fermentation. After pretreatment, most of the cellulose remained in the residue, ranging between 85.87% by the highest PSF (185°C, 15 min) and 92.90% obtained at the lowest PSF (185°C, 3 min). A larger part of starch, varying from 71.64% by the highest PSF to 78.28% by the lowest, was liberated into liquor part, leaving 8.05–11.74% in the residues. Xylan recovery in the residues increased from 44.25% at the highest PSF to 82.95% at the lowest. The recovery of xylan in liquor changed from 20.13% to 50.33%. Toxic test indicated that all the liquors from the five conditions were not toxic to the Baker’s yeast. Pretreatment under 195°C for 7 min had the similar PSF with that of 185°C for 15 min, and both gave the higher ethanol concentration of 19.92 and 19.98 g/L, respectively. The ethanol concentration from untreated maize silage was only 7.67 g/L.