Production optimization of food functional factor ergothioneine in wild‐type red yeast Rhodotorula mucilaginosaDL‐X01

BACKGROUND Ergothioneine (EGT) is a high‐value food functional factor that cannot be synthesized by humans and other vertebrates, and the low yield limits its application. RESULTS In this study, the optimal fermentation temperature, fermentation time, initial pH, inoculum age, and inoculation ratio on EGT biosynthesis of Rhodotorula mucilaginosa DL‐X01 were optimized. In addition, the effects of three key precursor substances – histidine, methionine, and cysteine – on fungal EGT synthesis were verified. The optimal conditions were further obtained by response surface optimization. The EGT yield of R. mucilaginosa DL‐X01 under optimal fermentation conditions reached 64.48 ± 2.30 mg L −1 at shake flask fermentation level. Finally, the yield was increased to 339.08 ± 3.31 mg L −1 (intracellular) by fed‐batch fermentation in a 5 L bioreactor. CONCLUSION To the best of our knowledge, this is the highest EGT yield ever reported in non‐recombinant strains. The fermentation strategy described in this study will promote the efficient biosynthesis of EGT in red yeast and its sustainable production in the food industry.