Metabolic engineering of Escherichia coli for the production of two-carbon primary amines

Primary amines are the industrially important chemicals widely used in the manufacture of dyes, pharmaceuticals, and agrochemicals. In this study, we developed metabolically engineered Escherichia coli strains for the efficient production of two-carbon primary amines, ethylamine and ethanolamine. For ethylamine production, metabolic pathways were optimized by enhancing flux toward the precursor l-alanine and by increasing the expression of a valine decarboxylase variant, VlmD^V94I. Subsequent optimization of fed-batch fermentation resulted in the production of 36.3 g/L of ethylamine with a productivity of 0.432 g/L/h and a yield of 0.184 g/g glucose. For ethanolamine production, the l-serine biosynthetic pathway was engineered by introducing a feedback-inhibition-resistant enzyme and deleting l-serine utilization pathways. Additional deletion of the iclR and ygeA genes further boosted precursor supply by activating the glyoxylate shunt and preventing the conversion of l-serine to d-serine. We then screened serine decarboxylases and identified Atsdc from Arabidopsis thaliana as the most effective enzyme. Under optimized fermentation conditions, the final strain produced 36.9 g/L of ethanolamine with a productivity of 1.04 g/L/h and a yield of 0.184 g/g glucose. These titers and productivities represent the highest reported values for bio-based production of two-carbon primary amines, demonstrating the strong industrial potential of microbial cell factories.