Progress in developing methods for lignin depolymerization and elucidating the associated mechanisms

The biorefining of sugar-based biomass has attracted increasing attention in response to the continuous depletion of fossil fuel reserves. The key to biorefinery is to choose a suitable way to pretreat lignocellulose to depolymerise lignin, thus releasing cellulose and hemicellulose, and the monosaccharides produced by subsequent enzymatic saccharification can be converted into high value-added compounds by biological or chemical methods, and lignin and its derivatives can also be used in the production of other biopolymers. Currently, numerous scholars have studied and developed processes for lignin depolymerisation. Still, the catalytic depolymerisation of lignin is complex, and the catalytic depolymerisation mechanism and the evolution of the chemical bonding still need to be determined. In this paper, we expect to classify the existing lignin depolymerisation methods and mechanisms reported in the literature and evaluate the advantages and disadvantages of each technique, as well as review the potential applications and challenges of lignin and its derivatives in the production of biopolymers, with the expectation of providing theoretical and technological support for the research and development of new efficient and stable lignin depolymerisation methods, and contributing to the development of biorefinery technology for lignocellulosic resources.