Metal Toxicity Assessment Upon Indigenous Thiobacillus thiooxidans BC1

Abstract

This study provides a first attempt to explain, in general terms, the toxicological threshold of Cd(II), Cu(II), and Zn(II) to Thiobacillus thiooxidans BC1. The most favorable pH for microbial growth and sulfate production of T. thiooxidans BC1 is ca. 2.0, as T. thiooxidans cells oxidize elemental sulfur well at acidic pH, which is required for growth. In addition, quantitative analysis on toxicity of divalent cadmium, copper, and zinc cations suggests a toxicity series of Cd > Cu >> Zn to T. thiooxidans BC1, as Zn(II) is termed nontoxic and the maximum treatable thresholds of Cd(II) and Cu(II) are ca. 300, 400 mg/L, respectively. This assessment clearly indicates operation outcome of metal bioleaching appearing in dichotomous guise (i.e., success or failure; "yes"/"no"), suggesting technological feasibility of biotreatment using acidophilic Thiobacilli T. thiooxidans BC1.