Unlocking corn stover for high utilization of fermentable sugars from both cellulose and hemicellulose: combining alkaline sodium sulfite and diluted citric acid pretreatment.

The efficient utilization of polysaccharides in lignocellulosic biomass is essential for the sustainable development of biorefineries. In this study, an innovative pretreatment approach was proposed to increase polysaccharide recovery and enzymatic digestibility of corn stover (CS) while reducing the bio-inhibitors in the hydrolysate. Fermentable monosaccharides derived from both cellulose and hemicellulose were efficiently produced by combined alkaline sodium sulfite and diluted citric acid pretreatment. The solid fraction of cellulose was recovered at 96.27 %, and the enzymatic glucose yield was up to 97.96 %, while the supernatant was rich in hemicellulose hydrolysate with very low inhibitor concentration, which could be utilized directly by microorganisms. In this context, one-pot enzymatic digestion and fermentation were successfully implemented without solid-liquid separation or detoxification, achieving a high ethanol yield of 0.24 g ethanol / g CS using brewer's yeast. This study provided an efficient method for the extraction of fermentable sugars for ethanol production from both the cellulose and hemicellulose fractions.