The Optimum Submerged Culture Condition of the Culinary-Medicinal White Jelly Mushroom (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 (EPS) 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 EPS. However, the quantity of EPS from different initial pH values (5-9) was not significantly different. Total polyphenol and β-glucan contents from every EPS 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%. EPS 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 EPS from T. fuciformis was noncytotoxic to mouse skin fibroblasts (NIH/3T3), and survival rates were more than 100% using MTT 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 EPS of T. fuciformis from submerged culture possess antioxidant properties and can be used as an alternative treatment for cell protection.