Metal removal rate of Thiobacillus thiooxidans without pre-secreted metabolite

Industrial microdevices are mostly manufactured by micromachining technology. Materials can be micromachined by various means, including mechanical, optical and chemical. The concerns of environmental impact and production costs are the inspirations behind one alternative method of micromachining, the use of bioleaching. The evaluation of a potential microorganism for the bioleaching machining technology is conducted in the current study. The dissolution of metals by the chemolithotrophic bacteria Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans is based on the physical contact between the bacteria and their extracellular secreted metabolites and metals. Cell growth quality during the machining process is also an important issue. The specific metal removal rate is a key criterion to characterize any industrial machining process, defined here by the mass removed in milligrams from 1 cm2 of machined area in 1 h by a solution with a cellular concentration of 1 × 108 cells/ml. The authors find that the specific metal removal rates for copper, aluminum and nickel are 0.5 mg/h, 0.06 mg/h and 0.93 mg/h, respectively.