Mushroom Biomass Waste Is a Source of the Antioxidants Ergothioneine and Glutathione

Abstract

Low-grade foodstuffs and unharvested materials from farms contribute a sizable amount of the waste that is disposed to landfills. Mushroom farms also contribute to this problem, as unmarketable fruiting bodies or parts of them are discarded in the waste stream. To limit the proportion of mushroom biomass waste that is deposited to landfills, we assessed whether culls of oyster and shiitake mushrooms and white button mushroom stem waste contain the antioxidants ergothioneine and glutathione. Enzyme-coupled spectrophotometric assays were used to assess the concentrations of glutathione (GSH) and its oxidized form glutathione disulfide in mushroom biomass waste. Ergothioneine analysis was performed with a high-performance liquid chromatography analysis. Most of the biomass waste contained ergothioneine and GSH concentrations that were on par with each one of the fresh mushrooms. Conversely, white button mushroom stem waste contained 77% less GSH than market-ready mushrooms. Finally, as a proof-of-concept cation exchange column chromatography was used to capture ergothioneine from oyster mushroom culls. This strategy has the potential to produce gram quantities of high value ergothioneine per tonne of mushroom biomass waste. These findings provide a strategy for the valorization of mushroom biomass waste and its diversion from landfills.