Development of a Reusable Na[DMSH] Ionic Liquid for Corn Cob Pretreatment: Structural Characterization and Enhanced Enzymatic Hydrolysis.

This study investigated the synthesis, reusability, and pretreatment performance of sodium dimethyl sulfoxide (Na[DMSH]) for corn cob biomass pretreatment and subsequent enzymatic hydrolysis. The chemical characteristics of the Na[DMSH] system were evaluated by NMR, while the retention of sodium and DMSO during repeated reuse was quantitatively monitored using ICP-OES and GC analysis, respectively. The pretreated corn cob was subsequently subjected to enzymatic hydrolysis, and the hydrolysis products were analyzed by LC-MS/MS using multiple reaction monitoring (MRM). Cellobiose was confirmed by comparison with an authentic standard based on retention time, precursor ion, and product ions. After 16 reuse cycles, the solid lignin content was 6.69 ± 0.27%, compared with 6.45 ± 0.14% for the non-reused Na[DMSH] treatment, while cellulose conversion remained high at 87.60 ± 0.13% and 88.43 ± 0.18%, respectively. The Na and DMSO retention after 16 cycles were 96.0% and 77.9%, respectively, indicating that the Na[DMSH]:DMSO system retained substantial chemical components during repeated use. LC-MS/MS analysis confirmed the presence of cellobiose, while HMF, furfural, and levulinic acid were not detected under the analytical conditions used. Overall, the results demonstrate that Na[DMSH] can be repeatedly reused for corn cob pretreatment while maintaining high delignification performance and enzymatic cellulose conversion. The findings provide experimental evidence supporting the potential of the Na[DMSH] system as a reusable pretreatment medium for lignocellulosic biomass.