The Optimum Submerged Culture Condition of the Culinary-Medicinal White Jelly Mushroom Tremella fuciformis (Tremellomycetes) and Its Antioxidant Properties

Tremella fuciformis is a natural edible and medicinal mushroom commercially available in Taiwan. In this study, the effects of initial pH, incubation time, and various media to optimize exopolysaccharide (BPS) production by T fuciformis were evaluated in shake flasks and a bioreactor. The antioxidant properties were investigated. The results showed that using potato dextrose broth medium (pH 9) and a 48-hour incubation time in a shake flask was the most efficient condition from which to obtain maximum BPS. However, the quantity of BPS from different initial pH values (5-9) was not significantly different. Total polyphenol and beta-glucan contents from every BPS sample (pH 5-9) were evaluated. T fuciformis polysaccharides (10 mg/mL, pH 9) could scavenge 40.63% of 1,1-diphenyl-2-picrylhydrazyl radicals. The chelating abilities of ferrous ion of all extracts reached more than 80%. BPS extract from the initial pH value of 9 showed the highest reducing power among the other pH values (half maximal effective concentration = 5.97 mg/mL). The BPS from T fuciformis was noncytotoxic to mouse skin fibroblasts (NIH/3T3), and survival rates were more than 100% using MT T assay. The samples were used to analyze the scavenging activity against oxidative damage induced by ultraviolet B radiation and hydrogen peroxide. The results showed the antioxidant activity occurred in a dose-dependent manner (P < 0.05). Furthermore, these findings prove that the BPS of T. fuciformis from submerged culture possess antioxidant properties and can be used as an alternative treatment for cell protection.