Metabolite transport and its impact on metabolic engineering approaches

Cells are the structural units of life and are separated from the environment by at least one cellular membrane consisting of a lipid bilayer. Thus, metabolite transport across cellular membranes is a key feature of living organisms. Specialized proteins or protein complexes mediate transport processes and are accessible to metabolic engineering approaches. Genetic modifications in metabolic engineering has mostly involved the deletion or overexpression of genes encoding for enzymes. The role of transporters has received much less attention, but as this special issue shows, it is a key factor to consider when rationally designing microbial cell factories. Transporters have been employed in metabolic engineering endeavors to target three fundamental aspects: Import of substrates , Export of products , Modification of intracellular fluxes.