Met. Eng. doi:10.1016/j.ymben.2014.05.007

Bio-based production of polyamide (nylon) precursors stands to eliminate waste and inefficiencies from petrochemical-based processes. The material properties of polymers incorporating diaminopentane have made this building block a target of metabolic engineering processes, but existing strategies have demonstrated only limited yields or include undesired byproducts. Kind et al. now report a strategy beginning with a known strain, Corynebacterium glutamicum LYS-12, that overproduces lysine. The addition of lysine decarboxylase and deletion of an N-acetyltransferase led to the desired product in 37% yield, whereas deletion of the lysine exporter gene and overexpression of a permease to increase diaminopentane export further increased the molar yield to 41%. Testing of the new strain DAP-16 in a fed-batch process led to a titer of 88 g L−1 within 50 h, with trehalose as the only major byproduct. During this process, the authors noted the importance of supplying sufficient ammonium, presumably to support high flux en route to lysine through diaminopimelate dehydrogenase, which has a low affinity for ammonium. Testing of several extraction conditions identified n-butanol as a suitable solvent, with a two-step distillation leading to >99.6% pure product. Examination of the diaminopentane polymerized with sebacic acid showed favorable comparisons to other polyamides, including a lower density and higher transparency though slightly lower heat distortion temperature.