Comparative Studies On Selenium Enrichment Characteristics Of Four Edible Fungi

Ultraviolet spectrophotometry was used to determine content of selenium in fungi with o-diaminobenzene hydrochloride as apparent color agent under 335nm detection wavelength. Analytical results showed that the average recovery was 103.7%and there was no significant difference between the values measured by this method and GB/T 5009.93-2003 method when the selenium content was among 5 to 30μg/g, indicating that this method was effective in determination of trace selenium in edible fungi.The selenium enrichment abilities of four edible fungi, Auricularia auricular, Pleurotus citrinipileatus, Lentinus edodes (Qingyuan) and Griflola frondosa were characterized. The selenium enrichment abilities were as follows:A. auricular> P. citrinipileatus> L. edodes> G. frondosa, while the selenium tolerance abilities were:A. auricular> G. frondosa> L. edodes> P. citrinipileatus. Liquid fermentation tests showed that relatively low selenium addition level (< 10μg/ml) not only promoted the mycelial growth but also enhanced the synthesis of polysaccharide and protein, while high concentration of selenium (> 100μg/ml) inhibited the fungal growth. 31.6-36.5%of selenium was organic selenium (bound to protein or polysaccharides) when about 2000μg/g of total selenium was accumulated in each of the four fungal mycelia, and selenium bound to proteins was more than that to polysaccharides. Microscopy examination showed that lots of red selenium particles with the diameter of 0.2-0.4μm were distributed in mycelia cells when A. auricular and P. citrinipileatus were cultivated in 50μg/g of selenium. That is to say, A. auricular and P. citrinipileatus tend to accumulate inorganic red selenium particles when grown under high concentration of selenium. L. edodes (Qingyuan) and G. frondosa accumulated fewer red selenium particles, thus, they were chosen for fruit body cultivation tests. Semi-commercial culture tests of L. edodes (Qingyuan) and G. frondosa in the solid medium with 2.85-22.83μg/g selenium demonstrated that there was a good linear relationship between the selenium in the mushroom and Na2SeO3 fortified in the compost. The correlation coefficient for L. edodes (Qingyuan) and G. frondosa were 0.9502 and 0.9397 in the first flush of mushroom, and 0.9894 and 0.9477 in the second flush of mushroom. Both flushes of mushrooms could be developed as good dietary selenium-enriched food when cultivated in the compost supplemented with 2.85μg/g of selenium as they could supply 109.1%and 73.6%of the daily selenium requirement of humans.Both of the fungal mycelium and fruit body could accumulate selenium. Selenium in the fruit body was transferred from mycelial cells. However, the fruit body had greater selenium enrichment ability than the fungal mycelia. Under a selenium addition level of about 10μg/ml (g), the selenium absorption efficiencies for mycelium of L. edodes (Qingyuan) and G. frondosa were 4.7%and 4.0%, while those for fruit body were 18.91%and 9.37%respectively.