Strategies for vine shoots valorization using hydrothermal treatment and delignification using deep eutectic solvents within a biorefinery scheme

Abstract

Vine shoots (VS) are one of the main residues generated by winemaking, usually disposed of by open-field burning, which contributes to environmental pollution. Owing to their high content of lignin, cellulose and hemicelluloses, these residues represent a valuable feedstock for the bio-based products production. This study assessed environmentally friendly pretreatment strategies based on deep eutectic solvents (DES) and water to enable the valorization of vine shoots within a biorefinery framework. Two processing routes were compared: direct DES delignification and a sequential configuration combining autohydrolysis followed by DES delignification. The eutectic mixture of choline chloride and formic acid (ChCl:FA) at 130 °C for 60 min was identified as the most suitable condition for full valorization of vine shoots. Direct DES delignification yielded a delignified VS with low lignin content (5.41 kg of lignin per100 kg VS) and glucan recovery yield of 68 %. In contrast, the sequential strategy enabled the recovery of a hemicelluloses-rich aqueous stream containing 43.8 g/L of oligosaccharides. Although glucan retention in the solid was slightly lower, 25 % of glucan was additionally recovered as glucooligosaccharides and 55 % of lignin was removed. Overall, the combined autohydrolysis-DES approach proved to be more suitable for an integrated biorefinery, allowing milder conditions, ∼50 % delignification efficiency, and multiproduct recovery including cellulose-rich solids, hemicellulosic oligosaccharides, and high-purity lignin.