Accumulation of zinc by the lentinus edodes (Berk.) mycelium cultivated in submerged culture.

To obtain rich in organic forms of zinc extracts of Lentinus edodes, possessing putative higher immunostimulating properties than actually used, mycelia were cultivated in zinc(II) enriched media. Culture media were enriched in zinc in concentration ranging from 0 to 90 microg mL(-1), added to the medium before inoculation. Total zinc concentration in submerged cultivated mycelial biomass has been determined by the use of atomic absorption spectroscopy method (AAS). Zinc concentration expressed in mg% of mycelial dry mass rose from 0,33 microg g(-1), estimated for mycelium cultivated in not enriched in Zn(II) medium, to 4,28 microg g(-1) for mycelium cultured in medium containing 50 microg mL(-1) of zinc. Higher than 50 microg mL(-1) concentration of Zn(II) in medium caused a decrease of zinc content in mycelial dry mass. Zinc concentration in the medium strongly affected the mycelial growth. Productivity of the mycelium rose proportionally to the increase of Zn(II) concentration in the medium. The highest mycelial growth was recorded for media containing Zn(II) in concentration of 50 microg mL(-1). Concentration of Zn(II) in the medium upper than 50 microg mL(-1) acted depressing on the mycelial growth. An optimal pH of the medium for zinc accumulation was estimated by cultivation of Lentinus edodes mycelia in media of pH ranging from 3,5 to 7, containing 50 microg mL(-1) of zinc(II). The optimal pH of the medium for zinc accumulation was 7. Proportionally to the increasing concentration of zinc(II) in the medium rose the percentage of this metal adsorbed on the cell surface, easy to remove by washing of the mycelium with the 0,05 molar EDTA solution. The value of the percentage of zinc adsorbed on the cell surface changed in the range from 30% to 70% for concentrations of Zn(II) in the medium rising from 20 to 110 microg mL(-1).