RELATIONSHIP BETWEEN THE SELENIUM, SELENOMETHIONINE, AND SELENOCYSTEINE CONTENT OF SUBMERGED CULTIVATED MYCELIUM OF Lentinula edodes (Berk.)

To obtain extracts rich in the organic forms of selenium with putative cancer-preventive properties more effective than those of selenizedyeast, Lentinula edodes mycelia were cultivated in media enriched with selenium at concentrations from 0 to 20 μg mL, by addition of sodium selenite either before inoculation or after three days of mycelial growth. The total selenium content of submerged cultivated mycelial biomass was determined by atomic absorption spectroscopy (AAS) and concentrations of selenomethionine and selenocysteine were determined by RP-HPLC. The concentration of selenium in the mycelia increased from 23 μg g dry weight (d.w.) for mycelia cultivated in media not enriched in selenium to 1800 μg g (d.w.) for mycelia cultivated in medium enriched with 20 μg mL selenium. The amount of selenomethionine in the cultivated biomass increased in proportion to the selenium content of the mycelium (concentration range 23–289 μg g d.w.) but the percentage of selenium accumulated as the selenoamino acid decreased. For selenium concentrations greater than 1 μg mL the selenocysteine content of the mycelial biomass does not depend directly on the concentration of selenium in the medium.