Investigation of the kinetics of selenium accumulation byLentinula edodes(Berk.) mycelial culture by use of reversed-phase high-performance liquid chromatography with fluorimetric detection

We hypothesized that extracts from selenium (Se)-enriched Lentinula edodes mycelia would have higher anticancer and immunostimulating properties than the nonenriched extracts currently used to treat cancer. Previously, we demonstrated that submerged cultivated mycelia of L. edodes accumulated Se from the cultivation medium very efficiently, more so than yeast. The objective of this study was to investigate the kinetics of Se accumulation by L. edodes mycelial culture. The L. edodes mycelia were cultivated in medium enriched with 20 μg mL−1 Se in a 10-L jar fermenter. Each day, a 100-mL sample was taken from the fermenter and the concentration of Se in the dried mycelia, in the filtered medium, and in the wash water was determined by reversed-phase high-performance liquid chromatography (RP HPLC). We adapted a widely used fluorimetric method based on derivatization with 2,3-diaminonaphthalene for analysis of Se for RP HPLC. Se recovery was determined on the basis of the theoretical amount of Se in the cultivation medium. To detect volatile selenium compounds released from the fermenter, the concentration of Se in the ethanol and in the activated charcoal used in the washers and exhaust filters was determined. The time-course of the Se content of dry mycelial biomass and in filtered medium indicated that the most effective accumulation of Se occurred at the beginning of the trophophase (log phase of growth), between the second and fourth days of cultivation. The Se concentration in mycelia peaked on day 7 (3041 μg g−1) and decreased thereafter in proportion to the increase in the concentration of Se in the ethanol and activated charcoal from the fermenter exhaust filters.