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Determination of optimal conditions for zinc-hyperaccumulation by Saccharomyces cerevisiae FF-10

Zinc is an essential trace element for many physiological functions in humans and animals. We have previously reported on the isolation of zinc-enriched Saccharomyces cerevisiae FF-10 from the tropical fruit Rambutan (Nephelium lappaceum L.). The present study was undertaken to investigate the influence of the optimal medium composition pertaining to carbon and nitrogen sources, amino acids, minerals, and different zinc compounds on zinc accumulation in FF-10 strain. The highest accumulation of zinc was obtained in a medium containing 2.0%(w/v) glucose, 5.0% yeast extract, and 0.05% ZnSO4 after cultivation at 110 rpm, 30°C, 72 h. Under these conditions, the 31,932 ppm zinc represented a 93-fold increase over the 339 ppm in the basal medium. The accumulation of zinc in yeast cells increased with the increase of supplemented concentrations (250–4,000 ppm) of zinc powder, zinc sulfate, zinc acetate, and zinc chloride in the culture medium, with the greatest accumulation evident at 4,000 ppm of zinc sulfate, zinc acetate, and zinc chloride. The zinc concentration in the medium strongly influenced FF-10 strain growth. In the presence of medium supplemented with 4,000 ppm zinc chloride, zinc accumulation by FF-10 strain increased by 445-fold to 150,892 ppm. From these results, the beat medium compositions for zinc accumulation in FF-10 yeast were obtained after cultivation with for 72 h in a medium containing 2% glucose, 5% yeast extract, and 0.04% ZnCl2.