Comparison of different alkali-based pretreatments of corn stover for improving enzymatic saccharification

Corn stover was treated with NaOH, NaOH + anthraquinone (AQ), NaOH + Na2SO3 (alkaline), NaOH + Na2SO3 (neutral), and NaOH + Na2S, respectively. The treated corn stover was subjected to hydrolysis with cellulase (20 FPU/g dry biomass) and β-glucosidase (10 IU/g dry biomass). Compared with other pretreatment methods, alkaline sodium sulfite pretreatment (ASSP) at a relatively low temperature of 140 °C provided for the best lignin removal of about 92%. After ASSP with 10 wt.% of the total alkali charge (Na2SO3:NaOH = 1:1) at 140 °C for 30 min and subsequent enzymatic hydrolysis, a total sugar yield of 78.2% was obtained on the basis of the amount of glucose and xylose released from raw corn stover. This yield was 24.0% higher than that achieved with NaOH only under the same conditions. Therefore, the supplement of Na2SO3 in alkali pretreatment can facilitate delignification and significantly improve the enzymatic saccharification.