Creative biological lignin conversion routes toward lignin valorization

Lignin, the largest renewable aromatic resource, is a promising alternative feedstock for the sustainable production of various chemicals, fuels, and materials. Despite this potential, lignin is characterized by heterogeneous and macromolecular structures that must be addressed. In this review, we present biological lignin conversion routes (BLCRs) that offer opportunities for overcoming these challenges, making lignin valorization feasible. Funneling heterogeneous aromatics via a ‘biological funnel’ offers a high-specificity bioconversion route for aromatic platform chemicals. The inherent aromaticity of lignin drives atom-economic functionalization routes toward aromatic natural product generation. By harnessing the ligninolytic capacities of specific microbial systems, powerful aromatic ring-opening routes can be developed to generate various value-added products. Thus, BLCRs hold the promise to make lignin valorization feasible and enable a lignocellulose-based bioeconomy. Biological lignin conversion routes (BLCRs) overcome the heterogeneous structures of lignin by harnessing the inherent capacity of ligninolytic microbes, opening the way to value-added products.Lignin depolymerization provides bioavailable aromatic derivatives suitable for downstream bioconversion.Atom-economic conversion routes are backbones in taping into the inherent aromaticity value of lignin to promote the microbial synthesis of valuable products.The scientific and technical evolution of synthetic biology enable the construction of microbial cell factories to improve lignin bioconversion.Lignin bioconversion would enable the economic viability of biorefineries and contribute to a sustainable lignocellulose-based bioeconomy.