Recent advances in microbial lignin degradation and upcycling of lignin-derived aromatic compounds

Lignin represents a promising and sustainable feedstock for the production of high-value products. However, its heterogeneity and recalcitrance pose a big challenge for efficient depolymerization and upcycling. This review highlights recent advances in microbial lignin valorization, focusing on three key steps: lignin depolymerization, metabolism of lignin-derived aromatic compounds, and valorization to target products. Recent progress in lignin depolymerization is enabling the discovery and optimization of more efficient and broadly specific ligninolytic enzymes, and highlights the critical role of auxiliary enzymes and quinone redox cycling in supporting ligninolytic activity. New catabolic mechanisms, transport systems, and transcriptional regulation networks for both dimeric and monomeric lignin-derived substrates expand our understanding of biological funneling pathways, and they offer valuable tools for designing more efficient microbial biocatalysts and biosensors. Emerging metabolic engineering and adaptive laboratory evolution strategies for creating robust microbial chassis capable of producing diverse value-added products from lignin-derived feedstocks are discussed.