Microwave-Assisted Deacetylation of Corn Stover by Sodium Carbonate to Improve Its Enzymatic Digestibility

Abstract Acetic acid released from acetylated hemicellulose during dilute acid pretreatment of corn stover can inhibit downstream bioconversion, while conventional strong alkali deacetylation often causes excessive carbohydrate loss and generates highly caustic spent liquor. A microwave-assisted sodium carbonate deacetylation process before dilute sulfuric acid pretreatment was developed in this study to reduce the potential formation of acetyl-derived inhibitors and improve the subsequent enzymatic hydrolysis of corn stover. The deacetylation achieved at optimal conditions (70 °C, 1.5 h, 3 wt % Na2CO3, solid–liquid ratio 1:15) was 88.53% along with 28.93% lignin removal and 9.32% hemicellulose loss. The enzymatic hydrolysis of deacetylated corn stover resulted in a glucan conversion of 72.98% at 10% solids loading, with a high glucose concentration of 54.49 g/L. No decrease in the glucan conversion was observed when the solids loading was increased from 2% to 10%, suggesting strong saccharification under process-relevant high-solids conditions. The sodium carbonate black liquor could maintain 64.5% of its original deacetylation performance after three rounds of recycling, corresponding to a deacetylation efficiency of 47.43%. Microwave-assisted sodium carbonate deacetylation provides an efficient way for biomass valorization.