Pathway optimization for effective heterologous synthesis of ergothioneine in Aspergillus niger

Ergothioneine (EGT) is a potent natural antioxidant, making it a promising candidate for potential applications in cosmetics, pharmaceuticals, and food industries. This study represents the successful heterologous synthesis of EGT in Aspergillus niger strain SH-2. By screening and co-expressing egt1 and egt2 genes from various sources, the combination of egt1 from Trichoderma reesei and egt2 from Neurospora crassa was the optimal EGT synthetic pathway. The synergistic effect of supplementing precursor resulted in a 34.70% increase in EGT production. However, the enhancement of precursor amino acid biosynthesis pathway played a negative role in the transcriptional level of EGT biosynthetic genes. Based on single-factor fermentation optimization, the maximum yield of EGT reached 3.12 g/L in 5-L bioreactor (144 h), the highest EGT titer heterologously synthesized in fungi. This study contributes to the field of heterologous EGT synthesis and offers an engineered A. niger strain OE4-T1N2 with potentially industrial application.