Comparative Study on Four Chemical Pretreatment Methods for an Efficient Saccharification of Corn Stover

Corn stover is a potential feedstock for cellulosic ethanol production. In this study, the performances of four chemical pretreatment methods, low-temperature moderate acid (LTMA), high-temperature dilute acid (HTDA), alkali pretreatment (AP), and sulfite pretreatment (SP), were compared in pretreating non-wood bioresource (corn stover) for an efficient saccharification. Under the investigated conditions, LTMA and HTDA could directly convert most xylan into xylose but had lower enzymatic digestibility from forming more fermentation inhibitors. AP pretreatment achieved better delignification, while its effect on removing xylan was very weak. SP pretreatment not only dissolved about 83.75 and 63.14% of xylan and lignin, respectively, but also caused less known inhibitors than acidic pretreatments. More interestingly, a large amount of xylo-oligosaccharides (about 17.12 g/L) was found in spent liquor from SP pretreatment, which is a potential high-value co-product. After 48 h of enzymatic hydrolysis, the cellulose saccharification yields were 24% for the LTMA substrate, 47% for the HTDA substrate, 60% for the SP substrate, and 65% for the AP substrate, respectively. These results suggested that SP pretreatment was a more suitable pretreatment method for bioethanol production of corn stover.