ELECTROCHEMICAL CULTIVATION OF THIOBACILLUS-FERROOXIDANS BY POTENTIALCONTROL

An iron oxidizing bacterium, Thiobacillus ferrooxidans can grow by oxi dation of Fe(II) to Fe(III). Electrochemical regeneration of Fe(II) fr om Fe(III) can supply the growth energy for the bacterium. Electrochem ical cultivation of T. ferrooxidans was carried out by the potential c ontrol method, The electrochemical regeneration occurred below 0.5 V v s, Ag/AgCl. The regenerated Fe(II) was consumed by the bacterium, whic h was observed by the cyclicvoltammetry of the soluble iron in the pre sence of the bacterium. The bacterium can be cultivated below the appl ied potential of 0.5 V. The bacterial growth rate increased at more ne gative potential in the range of 0.5 to 0 V. The growth rate depended on the reduction current at the applied potential range from 0 to -0.6 V. Hydrogen evolved at potentials more negative than -0.6 V. The bact erial growth rate was reflected by the electrochemical regeneration ra tes of Fe(II) which was determined by the rotatory ring-disk method. T he potential control method, which can control the electrochemical rea ction, would achieve a more efficient cultivation of the bacterium tha n the current control method which can waste current through the side reaction of hydrogen evolution. (C) 1997 Elsevier Science S.A.