Valorization of Camellia oleifera shell via taurine prehydrolysis coupled treatment with hydrated deep eutectic solvent

Abstract

The rapid advancement of the Camellia oleifera industry has resulted in a substantial generation of by-products in the form of Camellia oleifera shells (COS). COS exhibits a well-defined mesoporous structure and a high hemicellulose content, rendering it an ideal raw material for the production of xylo-oligosaccharides (XOS). Current biorefinery strategies aimed to produce XOS using organic acids primarily focused on the enhancement of XOS yield, while overlooking the specific functionalities that these organic acids contribute to the XOS products. Herein, taurine was employed to hydrolyze COS for the production of XOS. Subsequently, the taurine-hydrolyzed COS was treated using a hydrated deep eutectic solvent (DES) composed of maleic acid and choline chloride. The XOS with a degree of polymerization ranging from 2 to 6 (XOSDP2–6) yield reached a remarkable 56.4 % at 170 °C/30 min/0.2 M taurine, and the taurine-containing XOS demonstrated favorable biological safety and amelioration of developmental toxicity as determined by the zebrafish model. Then, the hydrated DES effectively removed lignin from taurine-hydrolyzed COS, leading to the generation of lignin with upgraded characteristics, including carboxylation. Finally, the two-step treated COS achieved a 92.5 % of cellulose conversion rate with a low cellulase dosage. The proposed biorefinery strategy facilitates the comprehensive and efficient utilization of COS.