Engineering pyridoxal kinase PdxY-integrated Escherichia coli strain and optimization for high-level 5-aminolevulinic acid production

Abstract

Recently, 5-aminolevulinic acid (ALA) has gained significant attention in research due to its extensive applications in agriculture, aquaculture, cosmetics, and photodynamic therapy for cancer. Microbial production of ALA is a green, high-efficient, and sustainable process. Herein, we have engineered a new strain of Escherichia coli called PdxY Integrative E. coliEnhancer (PIECE). In this strain, the super salvage pathway was fine-tuned to enhance the regeneration of pyridoxal 5′-phosphate (PLP), on which the activity of ALA synthase (ALAS) is highly dependent. The PIECE strain, harboring ALA synthase (ALAS) from Rhodobacter capsulatus, produced 1.99 g/L ALA and 5.15 g/L biomass, that was a 4.33-fold increase in ALA production and a 1.84-fold increase in biomass compared to the parent strain. The metabolic flux analysis indicated that PIECE would redirect more carbon into the tricarboxylic acid (TCA) cycle and generate more glycine and glutamate, thereby increasing the ALA and biomass. Finally, the maximum ALA yield of 8.21 g/L and a productivity of 0.228 g/L/h were obtained by using fed-batch fermentation. The results showed that PIECE was not only feasible for high-level ALA production but also had significant potential to reprogram the carbon flux in the TCA cycle to produce value-added chemicals in the future.