Selenium Biofortification Strategy Utilizing Liquid Culture of Tremella aurantialba Mycelia and Analysis of Its Nutrient Composition

Abstract:

[Objective] This study aims to establish an efficient selenium biofortification strategy based on the liquid culture of Tremella aurantialba (T. aurantialba) mycelia to enhance its selenium enrichment capacity. [Method] The changes of growth phenotype, metabolic behavior, and selenium enrichment characteristics of T. aurantialba mycelia were analyzed during the Na₂SeO₃-induced selenium biofortification process in liquid culture. [Result] Addition of 5 mg/kg and 10 mg/kg Na₂SeO₃ promoted mycelium growth, whereas Na₂SeO₃ with the mass fraction exceeding 10 mg/kg significantly inhibited the growth of T. aurantialba mycelia, with the inhibitory effect intensifying as Na₂SeO₃ mass fraction increased. Therefore, 5 mg/kg and 10 mg/kg of Na₂SeO₃ were selected. With the selenium-enrichment level and the bioconcentration factor (BCF) of the T. aurantialba mycelia as the primary indicators, single factor and orthogonal experiments were conducted to optimize the selenium biofortification parameters. The results demonstrated that in the case of the Na₂SeO₃ mass fraction being 5 mg/kg, the optimal culture conditions for T. aurantialba mycelia were Na₂SeO₃ addition on the 4th day, inoculum volume fraction of 2.25%, pH 6, and rotational speed of 150 r/min. In the case of the Na₂SeO₃ mass fraction being 10 mg/kg, the optimal culture conditions were Na₂SeO₃ addition on the 3rd day, inoculum volume fraction of 2.25%, pH 7, and rotational speed of 125 r/min. Under these optimized conditions and the Na₂SeO₃ mass fractions being 5 mg/kg and 10 mg/kg, T. aurantialba mycelia achieved selenium-enrichment levels of 148.24 mg/kg and 239.47 mg/kg, respectively, representing increases by 26.45% and 38.71% compared with those before optimization. Furthermore, the BCF reached 68.42% and 51.05%, which indicated improvements by 53.89% and 55.31%. Additionally, the analysis of the nutrient composition of selenium-enriched T. aurantialba mycelia revealed that proteins were the primary binding agents for selenium (>60%). The addition of selenium not only preserved the nutritional value of T. aurantialba mycelial protein but also enhanced the levels of umami amino acids (aspartate and glutamate). Moreover, SeMet was found to be the predominant selenium form in T. aurantialba mycelia. [Conclusion] This study provides a reference for future endeavors in enriching selenium in T. aurantialba for both edible and medicinal purposes and developing natural dietary supplements containing selenium.