Enhancing Lignin Model Compound Depolymerization Using Mediator-Enzyme Catalysis: A Sustainable Approach to C–C Bond Cleavage
Huan Zhang, Ren Liu, Yu Xin, Youran Li, Guiyang Shi, Rui Zhu, Liang Zhang
Abstract
The effective cleavage of C–C/C–O bonds in linkages of lignin with mild conditions and a green process was still a huge challenge for lignin valorization. Herein, the mediator–enzyme systems utilized in the depolymerization of lignin were developed. The C–C oxidation of β-O-4 lignin models was achieved through a mediator–enzyme systems. The carboxylic acid/ester-lipase was employed for the oxidation of ketone compounds. In the C–C bond oxidation process, Novozym 435 was used as the catalyst, and H 2 O 2 was used as the oxidant in the solvent of ethyl acetate for the reaction. The reaction conditions were optimized, and excellent conversion was achieved. The mediator-enzyme was active for the oxidative cleavages of various β-O-4 lignin model compounds substituted by different functional groups. Furthermore, Novozym 435 was employed as a recyclable biocatalyst, demonstrating its stability confirmed by SEM, FTIR, and XPS. This study introduces a mediator-enzyme strategy for lignin model compound depolymerization.