Mycobial enhancement of ergothioneine by submerged cultivation of edible mushroom mycelia and its application as an antioxidative compound

Ergothioneine (2-mercaptohistidine trimethylbetaine, ESH) in mushroom is one of bioactive and functional components. In the present study, a method of producing ESH within a short period and with high productivity was established by applying submerged fermentation of edible Shiitake mushroom (Lentinula edodes) mycelia. High-resolution mass spectrometry and online flow injection analysis of 2,2-diphenyl-1-picrylhydrazyl scavenging activity clearly confirmed that ESH was the most potent antioxidant in the mycelial extract. Among several mushroom mycelia, Shiitake produced the highest amount of ESH (0.60 mg/g dry weight (DW)). Optimisation of the culture medium was performed to achieve higher ESH production. The monosaccharide content in the medium, particularly fructose in combination with aspartic acid, was one of the factors that enhanced ESH production by 3.15-fold (1.89 mg/g DW). Individual supplementation of 2 mM methionine as an amino acid precursor yielded a significantly higher amount of ESH (3.45 mg/g DW) compared to that of the control medium (1.85 mg/g DW). The mycelial extracts containing ESH were effective in retarding the formation of secondary lipid oxidation products in the yellowtail red meat model during chilled storage as well as in the oxidation of linoleate and bleaching of beta-carotene in an oil-in-water emulsion system.