High-titer production of aromatic amines in metabolically engineered Escherichia coli

Aromatic amines are widely used in the pharmaceutical industry. Here, we reported the establishment of a bacterial platform for synthesizing three types of aromatic amines, namely, tyramine, dopamine, and phenylethylamine. Firstly, we expressed aromatic amino acid decarboxylase from Enterococcus faecium (pheDC) in an Escherichia coli strain with an increased shikimate (SHK) pathway flux toward L-tyrosine or L-phenylalanine synthesis. We found that glycerol served as a better carbon source than glucose, resulting in 940{+/-}46 mg/L tyramine from 4% glycerol. Next, the genes of lactate dehydrogenase (ldhA), formate acetyltransferase (pflB), phosphate acetyltransferase (pta), and alcohol dehydrogenase (adhE) were deleted to mitigate the fermentation byproduct formation. The tyramine level was further increased to 1.965{+/-}0.205 g/L in shake flasks, corresponding to 2.1 times improvement compared with that of the parental strain. By using a similar strategy, we also managed to produce 703{+/-}21 mg/L dopamine and 555{+/-}50 mg/L phenethylamine. In summary, we have demonstrated that the knockout of ldhA-pflB-pta-adhE is an effective strategy in improving aromatic amine productions, and achieved the highest aromatic amine titers in E. coli under shake flasks reported to date. Key pointsAromatic amino acid decarboxylase from E. faecium was used for aromatic amine production; ldhA, pflB, pta together with adhE were deleted to mitigate the fermentation byproduct formation; Our work represented the best aromatic amine titers reported in E. coli under shake flasks.