Microbial assimilation of lignin-derived aromatic compounds and conversion to value-added products

•Depolymerized lignin is a complex and variable mix of aromatic compounds.•Non-model microbes can convert these aromatic compounds to useful products.•Known microbial pathways can only assimilate a fraction of the potential lignin-derived substrates.•New products and microbial conversion pathways are needed that advantage lignin as a feedstock.•Tolerance to biomass-derived substrates and inhibitors is often limiting. Lignin is an abundant and sustainable source of aromatic compounds that can be converted to value-added products. However, lignin is underutilized, since depolymerization produces a complex mixture of aromatic compounds that is difficult to convert to a single product. Microbial conversion of mixed aromatic substrates provides a potential solution to this conversion challenge. Recent advances have expanded the range of lignin-derived aromatic substrates that can be assimilated and demonstrated efficient conversion via central metabolism to new potential products. The development of additional non-model microbial hosts and genetic tools for these hosts have accelerated engineering efforts. However, yields with real depolymerized lignin are still low, and additional work will be required to achieve viable conversion processes.