Cost-effective production of ergothioneine using Rhodotorula mucilaginosa DL-X01 from molasses and fish bone meal enzymatic hydrolysate

[Display omitted] •Untreated molasses could be utilized by R. mucilaginosa DL-X01 as carbon source.•Fish bone meal enzymatic hydrolysate was used to replace yeast extract and peptone.•The amount of molasses and fish bone meal added were optimized.•Feedstock cost of producing EGT is reduced by 331 % compared to using YPD broth. Ergothioneine (EGT) is a high-value natural antioxidant that cannot be synthesized by the human body. This study showed that Rhodotorula mucilaginosa DL-X01 can use untreated molasses and fish bone meal enzymatic hydrolysate as the substrates to synthesize EGT. By optimizing the growth conditions, the EGT yield reached 29.39 mg/L when molasses and fish bone meal (FBM) were added at 60 g/L and 400 g/L respectively. Finally, the EGT yield was increased to 216.25 mg/L by fed-batch fermentation in a 5 L bioreactor. Compared with the fermentation by yeast extract peptone dextrose medium, the feedstock cost of EGT production was reduced by 330.91 % by using molasses and FBM as substrates. These results showed that R. mucilaginosa DL-X01 can produce high-value EGT using two cheap processing by-products, molasses and FBM, which is of great significance for environmental protection and sustainable development.