A Preliminary Study On Selenium-enriched Cultivation Of Pleurotus Geesteranus

The aim of this paper was to cultivate Pleurotus geesteranus using the medium adding Se-Met to attain selenium-enriched fruit bodies, and analyze the crude protein, polysaccharide, selenium protein and polysaccharide selenium contents as well as properties antioxidant of the fruit bodies. So far, there were neither reports on P. geesteranus selenium-enriched cultivation of P. geesteranus, nor reports on the selenium-enriched cultivation of edible fungi using Se-Met as the selenium source. Therefore, this study was an exploration on new selenium sources those can be applied to cultivation of edible fungi. It was also helpful to get new selenium-enriched edible fungus products.A preliminary study on the effect of different mass fractions of Se-Met in medium on mycelial growth, fruiting and fruit bodies’selenium content of P. geesteranus was conducted. L9 (33) orthogonal test was used to optimize the medium formulations of P. geesteranus. The results showed that the low mass fraction of Sw-Met (0.05g/kg) in medium had a promoting influence on the mycelial growth of this fungus, while high mass fraction of Se-Met (0.7g/kg～1.0g/kg) had certain inhibitory effect. High mass fraction of Se-Met (0.7g/kg～1.0g/kg) restrain mycelial growth of P. geesteranus. When the Se-Met mass fraction in medium was 0g/kg-1.0g/kg, P. geesteranus could form normal fruit bodies. Lower mass fraction of Se-Met(0g/kg～0.4g/kg)had no significant effect on fruit bodies yield of P. geesteranus, but higher mass fraction of Se-Met (0.6g/kg～0.8g/kg)resulted in the decrease of mushroom yield. This indicated that higher mass fraction of Se-Met (0.6g/kg～0.8g/kg) had certain effect on fruit bodies’growth of P. geesteranus. By determining selenium content of P. geesteranus fruit bodies, we found that the selenium content in P. geesteranus fruit bodies had significant positive correlation with the Se-Met mass fraction in medium, and the selenium content of fruit bodies harvested in the medium containing 0.8g/kg Se-Met reached the highest value 11.43 μg/g. This article designed an orthogonal experiment with three factors and three levels to get the optimized medium formulations. Using the orthogonal matrix experimental method, the influence of the ratios of cottonseed hull to wheat bran, selenium content and sugar content in medium on P. geesteranus was discussed. The results showed that the optimal selenium-enriched medium formula was: cottonseed hull 88%, wheat bran 10%, gypsum 2%, Se-Met 0.4 g/kg, sugar 10 g/kg.Se-Met entering the fruit bodies were transformed most into protein selenium and polysaccharide selenium.53% to 57% of the total selenium present in the protein,23.26% to 24.98% of the total selenium present in the polysaccharides. This indicated that organic selenium existed mainly in the form of protein selenium. Selenium content in fruit bodies had a significant positive correlation with the polysaccharide content of fruit bodies, and had a significant negative correlation with the protein content.The antioxidant capability of selenium-rich P. geesteranus fruit bodies was evaluated. According to the DPPH scavenging activity, reducing power, ferrous ion chelating power and the ability to remove superoxide anion of ethanolic extracts from fruit bodies, it was shown that the effect of selenium contents in the fruiting bodies on its antioxidant properties was not significant. P. geesteranus fruit bodies with lower selenium content cultivated in the medium containing Se-Met of 0.4g/kg had higher antioxidant activity. Addition of lower amounts of Se-Met in medium was favorable to the enhancement of total phenol content in the fruiting bodies, but higher amounts of Se-Met in medium resulted in the decrease the total phenol content.