Common plastics such as polyamides are derived typically from petroleum or natural gas. Fossil-based polyamide production often involves toxic precursors or intermediates. By contrast, bio-based polyamides offer a realistic alternative. Bio-based routes to monomeric precursors of polyamides such as diamines, dicarboxylic acids, and omega-amino acids have been developed. Recent advances in the metabolic engineering of the biotechnologically relevant Escherichia coli and Corynebacterium glutamicum for the production of monoalkylamines such as omega-amino acids as well as diamines are presented.