Passive membrane transport of lignin-related compounds

Significance In nature, plants and microbes process substantial amounts of aromatic carbon for lignin biosynthesis and breakdown, respectively. These natural processes have important implications in the pursuit of lignin valorization, which is crucial for a vibrant, global bioeconomy. In both plant and microbial systems, an open question remains regarding how lignin-related aromatic compounds are transported across compartmental membranes, either by active membrane transporters or via passive membrane crossing. In this study, we predict that passive transport processes in plants and bacteria for uncharged aromatic compounds are likely sufficient for lignin biosynthesis and catabolism, thus implying that membrane translocation rates are controlled by compound delivery and utilization rates and membrane concentration gradients.