COSMO-RS assisted selection of eutectic solvents for lignin dissolution and enhanced laccase activity

Enzymatic lignin depolymerization provides a sustainable route for its valorization. Typically conducted in aqueous media, it faces technical limitations due to lignin's low solubility in water. Alternative media, such as aqueous solutions of eutectic solvents (ES), show excellent potential. However, selecting an optimal formulation that achieves both high lignin solubility and enhanced enzymatic activity remains a major challenge. This study aimed to establish an innovative method for screening and assessing the potential of ES in facilitating efficient lignin solubilization and enzymatic depolymerization, assisted by COSMO-RS and followed by experimental validation. Lignin solubility was predicted by calculating activity coefficient at infinite dilution of a lignin model compound in ES, while laccase activity was correlated with the water activity of the ES. A total of 10,638 combinations were screened, from which 22 showed promising properties and were selected for the experimental trials. Among those, an unexpected combination Acetamide:1,6-Hexanediol exhibited the highest lignin solubility of 46.5%w/w, achieving 111 % relative laccase activity and enhancing laccase-mediated depolymerization in the presence of mediators. For the best of our knowledge, this ES formulation was never addressed in literature for this purpose. Therefore, these findings offer promising insights and advance sustainable lignin valorization via enzymatic depolymerization.