Mercury bioremoval by Yarrowia strains isolated from sediments of mercury-polluted estuarine water

Difference in mercuric ion removal by resting and growing cells of two mercury-resistant yeast strains, identified as Yarrowia spp. (strains Idd1 and Idd2), were studied. Resting cells of strain Idd2 exhibited high maximum Hg²⁺ removal capacity (59 mg mercury per g dry cell weight [gdw⁻¹]) by adsorption than those of resting cells of strain Idd1 (32 mg gdw⁻¹). The resting cells of strain Idd2 exhibited a higher Hg²⁺ desorption capacity using CaCl₂ (68 %) and EDTA (48 %) than strain Idd1, depicting weaker binding of Hg²⁺ onto strain Idd2 unlike strain Idd1. The actively growing yeast cells showed opposite Hg removal characteristics to those of the resting cells. Strain Idd1 adsorbed less Hg²⁺ from culture medium supplemented with Hg²⁺ than strain Idd2. However, the growing strain Idd1 reduced and vaporized 27 % of supplemented Hg²⁺ as metallic mercury (Hg⁰), while the growing strains Idd2 vaporized 15 % of the supplemented Hg²⁺. These two yeast strains are potential biotechnological tools for the eventual bioremediation of polluted aquatic systems.