The abstract refers to work to analyse experimental results obtained in continuous growth and in batch, to figure out the parameters necessary to optimize FeSO//4 oxidation effectiveness by microorganisms. The bacterial strains used for the tests belong to genus Thiobacillus. To analyse the biomass growth rate and the FeSO//4 oxidation in solution, experimental trials in batch have been performed with an apparatus made up by a series of 12 ten liter reactors in a thermostatic bath. During these trials, several parameters influencing the growth rate have been determined. Moreover, some trials in continuous growth have been performed using a bench-scale fermentor. (Edited author abstract. )