Microgravity mutagenesis in E. coli: A molecular mechanism for high-yield cadaverine production

Abstract

Cadaverine serves as a monomer with significant potential in the industrial synthesis of polyamides, particularly nylon 5X. However, its broad application remains constrained by low microbial productivity and inherent cellular toxicity. Currently, the molecular mechanisms governing cadaverine production and tolerance in E. coli remain incompletely elucidated. In this study, we developed two engineered strains, ΔE. coli LdcEt-D8 and ΔE. coli LdcEt-MG-I6, through microgravity mutagenesis and adaptive laboratory evolution. These strains exhibited remarkable performance enhancements: cadaverine concentration (g L⁻¹) in the whole-cell catalytic reaction increased by 191% and 412%, respectively, while cadaverine tolerance rose by 139% and 193%, relative to the parental strain E. coli LdcEt. Whole genome and transcriptomic analyses revealed that enhanced central carbon metabolism pathway contributed to increased cadaverine production. Concurrent upregulation of amino acid metabolism pathway, fatty acid synthesis pathway, and genetic information repair pathway correlated strongly with improved cadaverine tolerance. Validation experiments on mutant genes confirmed that individual overexpression of purA, accC, holB, cysM, and prps in E. coli BL21(DE3) consistently enhanced cadaverine production, underscoring the indispensable role of mutant genes in the biosynthesis pathway. Collectively, these findings provide insight into the molecular mechanism behind the improved production in mutant strains, as well as decoding the transcriptomic landscape, which provides key targets for advancing whole-cell catalytic synthesis of cadaverine in E. coli.