Enhancement of In Situ Enzymatic Saccharification of Corn Stover by a Stepwise Sodium Hydroxide and Organic Acid Pretreatment.

A stepwise pretreatment method that combines sodium hydroxide and organic acid pretreatments was proposed and investigated to maximize the recovery of main constituents of lignocellulose. The sodium hydroxide pretreatment was firstly optimized by a designed orthogonal experiment with the optimum pretreatment conditions determined as 1 wt% NaOH at 70 °C for 1 h, and 60.42 % of lignin was successfully removed during this stage. In the second stage, 0.5 % acetic acid was selected to pretreat the first-stage solid residue at 80 °C for 40 min in order to decompose hemicelluloses to soluble oligomers or monomers. Then, the whole slurry was subjected to in situ enzymatic saccharification by cellullase with a supplementation of xylanase to further degrade the xylooligosaccharides generated during the acetic acid pretreatment. The maximum reducing sugar and glucose yields achieved were 20.74 and 12.03 g/L, respectively. Furthermore, rapid ethanol fermentation and a yield of 80.3 % also testified this pretreatment method, and the in situ saccharification did not bring any negative impact on ethanol fermentation and has a broad application prospect.