Accelerated 5-aminolevulinic acid biosynthesis by coupling aconitase and ALA synthase in engineered Escherichia coli

In recent years, 5-aminolevulinic acid (5-ALA) has attracted significant interest due to its roles as a photodynamic prodrug and an antiviral agent. In this study, we present a new approach using aconitase A from Escherichia coli Nissle 1917 (EcNAcnA), renowned for its exceptional activity and conjunction with ALA synthase from Rhodobacter capsulatus (RcALAS) to enhance 5-ALA production in an engineered chassis. Expression of EcNAcnA and RcALAS via dual plasmids led to a 59 % increase in 5-ALA yield, reaching up to 6.645 g/L. Diverse 5-ALA production levels were observed with different combinations of promoters and replication origins for both genes. Subsequently, an all-in-one plasmid with a high copy number, designated as RcNN, was introduced into the genomic engineering RcI strain. This resulted in the production of 24.5 g/L 5-ALA with a productivity of 0.907 g/L/h in a bioreactor under pH control and glucose feeding over 27 h. To the best of our knowledge, this is the first study to enhance 5-ALA biosynthesis by applying a superior aconitase variant from E. coli Nissle 1917, which enhances isocitrate production in the tricarboxylic acid (TCA) cycle and alleviates reactive oxygen species (ROS), thereby promoting 5-ALA accumulation effectively.