Toward more efficient ergothioneine production using the fungal ergothioneine biosynthetic pathway

Background Ergothioneine (ERG) is a potent histidine-derived antioxidant that confers health-promoting effects. Only certain bacteria and fungi can biosynthesize ERG, but the ERG productivity in natural producers is low. ERG overproduction through genetic engineering represents an efficient and cost-effective manufacturing strategy. Results Here, we showed that Trichoderma reesei can synthesize ERG during conidiogenesis and hyphal growth. Co-expression of two ERG biosynthesis genes (tregt1 and tregt2) from T. reesei enabled E. coli to generate 70.59 mg/L ERG at the shaking flask level after 48 h of whole-cell biocatalysis, whereas minor amounts of ERG were synthesized by the recombinant E. coli strain bearing only the tregt1 gene. By fed-batch fermentation, the extracellular ERG production reached 4.34 g/L after 143 h of cultivation in a 2-L jar fermenter, which is the highest level of ERG production reported thus far. Similarly, ERG synthesis also occurred in the E. coli strain engineered with the two well-characterized genes from N. crassa and the ERG productivity was up to 4.22 g/L after 143 h of cultivation under the above-mentioned conditions. Conclusions Our results showed that the overproduction of ERG in E. coli could be achieved through two-enzymatic steps, demonstrating high efficiency of the fungal ERG biosynthetic pathway. Meanwhile, this work offers a more promising approach for the industrial production of ERG.

Automated summary

Through genetic engineering, genes from Trichoderma reesei and N. crassa were successfully transferred to E. coli, enabling efficient synthesis of ergothioneine. The combination of genes from T. reesei showed the best synthesis efficiency, reaching up to 4.34 g/L per liter.