Enhancement and balance of 1,4-butanediamine biosynthesis in Escherichia coli based on modular metabolic engineering

1,4-Butanediamine is an important raw material for the synthesis of engineering plastics such as Polyamide 46 with excellent performance, which is widely used in automotive, electronics and machinery manufacturing industries. In this study, Escherichia coli BL21(DE3) was used as the starting strain to systematically modify the 1,4-butanediamine biosynthesis pathway using a modular strategy. 1,4-Butanediamine biosynthesis was re-divided into two modules: 1,4-butanediamine production module and α-ketoglutaric acid production module. By controlling the expression intensity of genes pykF, ppc, aceEF, gltA, icdA and gdhA, argD, argCB, argJ, ODC10, a recombinant producing 1,4-butanediamine strain PKT was obtained, achieving a yield of 862.82 mg/L of 1,4-butanediamine, which increased 8.62-fold compared to that of Escherichia coli BL21(DE3). Then, the fermentation medium of PKT strain was optimized. After 24 h of fermentation, the yield of 1,4-butanediamine reached 1843.60 mg/L, representing a 16.23-fold increase over the original strain. Furthermore, non-target metabolomics analysis was used to analyze the changes of metabolites during the efficient synthesis of 1,4-butanediamine by the recombinant strain PKT. The results showed that the total number of differential metabolites detected was 653. Differential metabolite pathway analysis showed that there were 9 differential metabolites in the 1,4-butanediamine synthesis pathway, with 5 involved in its synthesis pathway and 4 in its degradation branch. These differences in metabolites provide a theoretical basis for the modification of recombinant strains. The green production of 1,4- butanediamine by microbial cell factories through fermentation is the future direction. This research provides a theoretical guidance of building high yield 1,4-butanediamine engineering strains.