Acidic and alkaline deep eutectic solvents (DESs) pretreatment of grapevine: Component analysis, characterization, lignin structural analysis, and antioxidant properties

• Published in: International journal of biological macromolecules 2023-05, Vol.236, p.123977-123977, Article 123977
• Main Authors: Zhu, Yuan, Yang, Tian-Xiao, Qi, Ben-Kun, Li, Hang, Zhao, Qing-Sheng, Zhao, Bing
• Format: Article
• Language: English
• Subjects: Antioxidant activity; Antioxidants - pharmacology; Biomass; Choline - chemistry; Deep Eutectic Solvents; DES pretreatment; Hydrolysis; Lignin; Lignin - chemistry; Phenols; Solvents - chemistry; Structure characterization
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2023.123977

Deep eutectic solvents (DESs) have been extensively applied to pretreat lignocellulose; however, comparative research on acidic and alkaline DES pretreatment is relatively lacking. Herein, pretreatment of grapevine agricultural by-products with seven DESs were compared in terms of removal of lignin and hemicellulose and component analysis of the pretreated residues. Among the tested DESs, both acidic choline chloride-lactic (CHCl-LA), and alkaline potassium carbonate-ethylene glycol (K2CO3-EG) were effective in delignification. Thereafter, the CHCl-LA and K2CO3-EG extracted lignin was compared by analyzing their physicochemical structure changes and antioxidant properties. The results showed that the thermal stability, molecular weight, and phenol hydroxyl percentage of CHCl-LA lignin were inferior to K2CO3-EG lignin. It was found that the high antioxidant activity of K2CO3-EG lignin was mainly attributed to the abundant phenol hydroxyl, guaiacyl (G), and para-hydroxy-phenyl (H). By comparing acidic and alkaline DES pretreatments and their lignin nuances in biorefining, novel insights are derived for the scheduling and selection of DES for lignocellulosic pretreatment. •CHCl-LA pretreatment has a great advantage in removing lignin and hemicellulose.•K2CO3-EG pretreatment benefits lignin structure and thermal stability preservation.•Significant chemical shift in the guaiacyl lignin unit of K2CO3-EG lignin.•K2CO3-EG lignin retains more phenol hydroxyl have better antioxidant properties.