Fundamental Study on Biomachining : Machining of Metals by Thiobacillus ferrooxidans

In this paper, we present the possibility of biological machining by bacteria as a new technique for metal removal. There are some kinds of chemolithotrophic bacteria which gain energy from inorganic matter and fix carbon dioxide of the air. Among them, there is a particular bacteria, Thiobacillus ferrooxidans, which "eats" metals. Machining of grooves on pure iron and pure copper by Thiobacillus ferrooxidans is experimentally investigated. The experimental analysis made it clear that biomachining was possible, since the depth of the groove generated on the workpiece increased approximately proportionally to the machining time. Furthermore, electric field assisted biomachining proved to be even more effective, because the removal rate became much higher under an electric field.