Innovative use of Thiobacillus ferrooxidans for the biological machining of metals

Preliminary results on the novel use of the bacterium Thiobacillus ferrooxi dans (ATCC13598 and ATCC33020) for the micro-machining (or biomachining) of metals are reported. Biomachining is a controlled microbiological process to selectively form microstructures on a metal work-piece by metal removal (or dissolution) using microorganisms. Applying copper and mild steel as wo rk-pieces, it was shown that the mass removed increased proportionately wit h machining time. In another experiment, the work-pieces were coated with o rganic photo-resistive materials to mask (i.e. protect) certain regions of the metals, thereby defining the microstructure to be formed. The unmasked regions were: successfully biomachined; the final machined profile was show n to be similar to the coating image on the original metal. Although biomac hining proceeded at a slower rate: than chemical machining, the undesired l eaching of the metal in the region under the masked area (termed undercutti ng) was not as severely encountered when compared with the latter. This wor k demonstrates the potential use of microorganisms for the biomachining of metals. As a "green process", the innovative use of T. ferrooxidans for the micro-machining of metals opens up the possibility of biomachining as an a lternative to conventional metal processing.