Advances in microbial lignin degradation and its applications

Lignocellulosic biomass represents a crucial resource for achieving sustainable development by replacing petroleum-based production systems. Lignin, a major component of plant cell walls, has significant potential as a bioresource; however, it is an obstacle in lignocellulosic biomass utilization due to its recalcitrance. Consequently, decomposition or removal of lignin is a crucial step to utilize cell wall components. In nature, lignin may be degraded via two stages: depolymerization and the mineralization of the resulting heterogeneous low-molecular-weight aromatic species. Microbial enzymes responsible for the former could be attractive tools for lignin decomposition during biomass pretreatment, and enzymes involved in the latter are useful for lignin valorization through the production of value-added chemicals. Moreover, specific microbial enzymes could reduce the recalcitrance of lignocellulosic biomass via plant cell wall bioengineering. This review focuses on microbial enzymes that are responsible for lignin degradation and on their applications to biological lignocellulosics pretreatment and biotechnological lignin engineering.