Mild γ-Butyrolactone/Water Pretreatment for Highly Efficient Sugar Production from Corn Stover

In this study, γ-butyrolactone/water (GBL/H₂O) was explored as a mild, efficient, and cost-effective binary solvent pretreatment to enhance hydrolyzability of corn stover (CS). Key pretreatment parameters-reaction time, temperature, and H₂SO₄ concentration-were systematically investigated for their effects on the physicochemical properties of CS. Specifically, increased temperature and acid concentration significantly decreased cellulose crystallinity (from 1.39 for untreated CS to 1.04 for CS pretreated by GBL/H₂O with 100 mM H₂SO₄ at 120 °C for 1 h) and promoted lignin removal (47.3% for CS pretreated by GBL/H₂O with 150 mM H₂SO₄ at 120 °C for 1 h). Acknowledging the cellulase's limited hydrolysis efficiency, a dual-enzyme scheme using a low cellulase dosage (10 FPU/g) supplemented with β-glucosidase or xylanase was tested, enhancing hydrolysis of CS pretreated under low temperature-long duration and high temperature-short duration conditions, respectively. Optimum sugar release was obtained from CS pretreated with GBL/H₂O and 150 mM H₂SO₄ at 120 °C for 1 h, achieving 98% glucan and 82.3% xylan conversion, compared with 53.9% and 17% of glucan and xylan conversion from untreated CS. GBL/H₂O pretreatment outperformed other binary systems in literature, achieving the highest sugar conversions with lower enzyme loading. These results highlight the potential of GBL/H₂O pretreatment for efficient biomass conversion, contributing to the goals of the green economy.