A Study On Selenium Fortification And Its Key Issues On Oyster Mushroom (Pleurotus Geesteranus)

Selenium (Se) is an essential trace element for human-beings and animals, and is still an important component, the most powerful antioxidant enzymes, of glutathione peroxidase (GSH-Px) in the human body and even associated with normal metabolism and health effect by its concentration in animals and humans. Furthermore, Se is vital in anti-oxidizing, anti-aging, antitumorigenesis, boosting immunity, preventing cardiovascular diseases and fighting against diseases involved in virus. Therefore, it has been the subject of intensive research in bio-medicine and food science to develop the edible or medicinal Se-enriched products with low production cost in recent years. The present study was undertaken to investigate on Se of different sources, chemical speciation and synergistic effects with other heavy metals, by selecting a rare mushroom species, oyster mushroom(Pleurotus geesteranus), for the solution to the scientific and technological problems involved. The findings suggest that:(1) After Se-fortification with Na2SeO3 and Na2SeO4, the Se concentrations in the fruiting bodies of P. geesteranus were increased up to respectively 223.8 mg/kg and 396.7 mg/kg,1097 and 1983 times higher than that of control group, by measurement of dry samples, which showed that P. geesteranus is an equal choice edible species of fungi, for it is highly subjected to selenium enrichment and endurance. Furthermore, the Relative Standard Deviations (RSD) of Se concentrations in the fruiting bodies was found individually lower than 30% in Na2SeO4-fortification group and below 50% in Na2SeO3-fortification group. This further demonstrates that the Se-fortification method could be reliable for industrial purpose.(2) The efficiency of inorganic Se (Na2SeO4, Na2SeO3) by P. geesteranus was less than 33% and generally hovering around 10%. No significant differences were found between the diverse two Se sources, though, the bioavailability of organic Se in the corncob powder achieved up to 62.8%.(3) P. geesteranus itself can totally convert the inorganic selenium from the culture community into organic Se that is atoxigenic and safe to our humans. Moreover, the occurrence of Se in P. geesteranus fruiting bodies is commonly and naturally in the forms of selenomethionine (SeMet) with more than 70% and organic ones, including selenocystine (SeCys2), Se-methyl selenocysteine (SeMeCys) and some other unknown organic selenium compounds. (4) The arsenic (As) concentration detected in P. geesteranus fruiting bodies of dry samples was lower than 400μg/kg, which answers for the provisions defined in the National Arsenic Limit Standard, and further, Se-fortification will result in no accumulation of As in the fruiting bodies.In summary, the present study could provide technique basis for the establishment of P. geesteranus Se-fortified system as well as theoretical foundation for the development of Se-enriched edible fungi.