Efficient fractionation of corn stover via 4-CSA-based ternary deep eutectic solvent for cellulose valorization and recyclable enzyme immobilization in isoquercitrin bio-production

Abstract

Corn stover (CS) is the primary bioresource of agricultural biomass residue in China. Its natural degradation releases significant amounts of greenhouse gases and can lead to potential soil environmental issues. Directed depolymerization of corn stover is crucial for the high-value utilization of its chemical components, addressing the current urgent need for comprehensive biomass utilization. An efficient pretreatment strategy was employed using a 4-Chlorobenzenesulfonic acid (4-CSA) based three-constituent deep eutectic solvent (t-DES) for the fractionation of CS. Increasing the molarity of 4-CSA and the pretreatment temperature improved fractionation efficiency, resulting in over 95.74 % hemicellulose removal, 91.08 % delignification, and 91 % cellulose retention using t-DES (ChCl-BDO-4-CSA molar ratio of 1:1:1) at 100 °C for 30 minutes. The cellulose-enriched fractions (CRF) not only exhibited a high glucose yield of 91.8 % but also served as effective enzyme immobilized carriers with a selective adsorption capability of 17.895 mg·g⁻¹ with carbohydrate-binding modules (CBM). The impact of lignin content in CRF on the adsorption capability towards CBM-SpyCatcher003 was investigated. Subsequently, the immobilized podoRha, developed using CRF, recombinant CBM-spycatcher003, and recombinant podoRha-spytag003, exhibited recyclability. This system was successfully utilized in the biotransformation of rutin (15 mM) with a molar conversion rate of 98.89 % and an isoquercitin productivity of 3.278 g·L⁻¹·h⁻¹. This study presents an effective method for the fractionation of CS and offers a potential application for CRF as enzyme immobilized carriers.