Selenite is valuable in the production of Se-enriched Lentinula edodes

Selenium (Se) is an essential micronutrient for humans and animals. It acts as the active center of selenoenzymes and selenoproteins and plays an important role in energy metabolism and gene expression in organisms (Izquierdo, Casas, & Herrero, 2010). Therefore, it has many important biological functions, such as antioxidant, immunoregulatory, and antagonistic roles (Roman, Jitaru, & Barbante, 2014). However, approximately 0.5–1?billion people in the world still face Se deficiency (Winkel et al., 2012). Hence, obtaining a safe and efficient source of dietary Se has always been a research hotspot.

The intake speciation of Se is an important factor to determine its toxicity, nutritional value, and metabolic pathways, which also influence its distribution in tissues (Gergely, Kubachka, Mounicou, Fodor, & Caruso, 2006). For example, Se mainly exists in the form of SeMet in wheat, rice, and other grain crops (Hart et al., 2011), while it is mainly accumulated as MeSeCys and γ-glu-MeSeCys in Allium plants (Marschall et al., 2017). Edible fungi are the second largest category of vegetables with fine texture of fruit bodies and are rich in amino acids, proteins, and nutrients. By incorporating Se into active macromolecules during substance metabolism in cells, the mycelium of edible fungi can transform inorganic Se (from the substrate) into selenoproteins, selenopolysaccharides, and other organic forms, which possess high bioavailability and low toxicity (Maseko, Howell, Dunshea, &Ng, 2014)

In a recent study conducted by Chinese researchers from Northwest A&F University, . different concentrations of selenite, selenate and Se-yeast were injected as Se-supplements into substrates to produce Se-enriched Lentinula edodes. The Se content and its speciation distribution in the fruit bodies of Lentinula edodes were analysed at different harvest times. Results indicate that Se concentrations of L. edodes increased first and then decreased over time. Based on Se accumulation in L. edodes, selenium use efficiency was ranked as selenite?>?selenate?>?Se-yeast. SeMet was the predominant Se speciation in the fruit bodies of L. edodes. SeMet made up the biggest proportion of total Se content and increased with application time for selenite and selenate treatments, whereas no significant change was found for Se-yeast treatment.

As shown in this study, supplemented selenite was most efficiently utilized, followed by selenate and Se-yeast. Also, exogenous Se from the substrates was transformed and ultimately accumulated in the fruit bodies of L. edodes mainly in organic forms (especially SeMet) regardless of inorganic or organic Se supplementation of the cultivation substrate. Thus, selenite is valuable in the actual production of Se-enriched edible fungi. This study also demonstrates that Se-enriched L. edodes is a good source of dietary Se.

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