Mild alkaline presoaking and organosolv pretreatment of corn stover and their impacts on corn stover composition, structure, and digestibility

•Mild alkaline presoaking and organosolv pretreatment of CS were evaluated.•The maximum total sugar yield achieved was 98.6% with a moderate enzyme loading.•Large amounts of lignin and hemicelluloses were removed after pretreatment.•The SSA and PV significantly enlarged after pretreatment.•The CrI of the pretreated residue increased but the cellulose was highly digestible.

An efficient strategy was developed in current work for biochemical conversion of carbohydrates of corn stover into monosaccharides. Corn stover was first presoaked in mild alkaline solution (1% Na2S) under 40 °C for 4 h, after which about 35.3% of the lignin was successfully removed while the specific surface area was notably enlarged. Then the presoaked solids were subjected to organosolv pretreatment that employed 20% methanol with an addition of 0.2% HCl as catalyst at 160 °C for 20 min, and the maximum total sugar yield of the pretreated corn stover achieved was 98.6%. The intact structure of corn stover was disrupted by this two-step process, which resulted in a porous but crystalline structure of the regenerated solids that were mainly composed of cellulose. The enlarged specific surface area and increased accessibility made the regenerated solids highly digestible by a moderate enzyme loading.

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