Submerged Cultivation of Mycelium with High Ergothioneine Content from the Culinary-Medicinal King Oyster Mushroom Pleurotus eryngii (Higher Basidiomycetes) and its Composition

The culinary-medicinal king oyster mushroom, Pleurotus eryngii, was used to produce mycelia with high ergothioneine content using a one-factor-at-a-time method. The optimal culture conditions for mycelia harvested at day 14 were 25°C, 10% inoculation rate, 2% glucose, 0.5% yeast extract, and no adjustment to the initial pH value. With histidine or amino acid mix added, biomasses and the ergothioneine content of mycelia were higher than those of the control. The ergothioneine content of mycelia harvested at days 16−20 were higher than that of mycelia harvested at day 14. In addition, the ergothioneine content of mycelia from the fermentor (5.84−5.76 mg/g) was much higher than that of mycelia from the shaken flask (4.93−5.04 mg/g). Mycelia with high ergothioneine content showed a profile of proximate composition similar to that of regular mycelia but lost its characteristic umami taste. Overall, mycelia high in ergothioneine could be prepared by optimal culture conditions, the addition of precursors, prolonged harvest, and aeration in the fermentor.