Alternative Lime Pretreatment of Corn Stover for Second-Generation Bioethanol Production

In this work, a delignification process, using lime (Ca(OH)2) as an alternative alkali, was evaluated to improve enzymatic saccharification of corn stover cellulose, with the final goal of obtaining second-generation bioethanol. For that, an experimental design was conducted in order to assay the effect of temperature, lime loading, and time on the corn stover fractionation and enzymatic susceptibility of cellulose. Under conditions evaluated, lime pretreatment was selective for the recovery of cellulose (average of 91%) and xylan (average of 75.3%) in the solid phase. In addition, operating in mild conditions, a delignification up to 40% was also attained. On the other hand, a maximal cellulose-to-glucose conversion (CGCMAX) of 89.5% was achieved using the solid, resulting from the treatment carried out at 90 °C for 5 h and lime loading of 0.4 g of Ca(OH)2/g of corn stover. Finally, under selected conditions of pretreatment, 28.7 g/L (or 3.6% v/v) of bioethanol was produced (corresponding to 72.4% of ethanol conversion) by simultaneous saccharification and fermentation. Hence, the process, based on an alternative alkali proposed in this work, allowed the successful production of biofuel from the important and abundant agro-industrial residue of corn stover.