Growth characteristics of Acidithiobacillus thiooxidans in different sulfur concentrations

The growth characteristics of sulfur-oxidizing bacteria, Acidithiobacillus thiooxidans AZ11, MET, and TAS were investigated in mineral salt media supplemented with elemental sulfur of 1-50 g L^-1. The sulfur oxidation rates of A. thiooxidans MET and TAS increased highly with increasing sulfur concentration up to 10 g L^-1, but the rates increased slowly in sulfur concentration over 10 g L^-1. A. thiooxidans AZ11 showed the parallel increase of sulfur oxidation rate until sulfur concentration increased up to 40 g L^-1. The maximum sulfur oxidation rates (V_max) of AZ11, MET and TAS were 1.88, 1.38 and 0.43 g S L^-1 d ^_1, respectively. The maximum specific growth rates (μ_max) of AZ11, MET, and TAS were 0.33 d^-1, 0.30 d ^-1 and 0.45 d^-1, respectively. Although MET and TAS couldn't grow at sulfate concentration of 40 g L^-1, AZ11 could grow in the presence of 58 g L^-1 sulfate, the final oxidation product of elemental sulfur.