Efficient production of Ergothioneine via an optimized allogenous assembly of the ERG synthesis pathway in Escherichia coli BL21

Ergothioneine (ERG) is a potent antioxidant with applications in nutrition, pharmaceuticals, dermatology, and related fields. However, its large-scale production is constrained by low yields and high costs linked to extraction and chemical synthesis. Microbial fermentation offers a promising alternative. In this study, a truncated NcEgt1–1 from Neurospora crassa and CtEgtB from Chloracidobacterium thermophilum were fused to convert L-histidine and L-cysteine into hercynylcysteine sulfoxide, subsequently catalyzed by MsEgtE from Mycobacterium smegmatis to produce ERG. Initial expression in Escherichia coli yielded 87.02 mg/L of ERG. With the use of a rigid linker-EAAAK, the ERG titer increased to 144 mg/L. Further amino acid modifications in NcEgt1–1 resulted in the mutant strain M3–02, producing 325 mg/L of ERG. Fed-batch fermentation in a 5-L bioreactor achieved an ERG yield of 790 mg/L with a productivity of 9 mg/L/h. Iterative mutations of CtEgtB further increased ERG production to 478 mg/L in shake flasks and 790 mg/L in the bioreactor, with productivity rising to 14.9 mg/L/h. This study presents an engineered strain with significant ERG production potential, suitable for industrial application.