Oxygen mass transfer requirements during ferrous iron oxidation by Thiobacillus ferrooxidans under controlled pH conditions

The ferrous iron oxidation by the bacterium Thiobacillus ferrooxidans B5 wa s studied under different aeration conditions at constant pH (1.8 and 2.0) in three types of bioreactors (shake flasks, a bubble column and a stirred tank). The main goal was to reflect the effects of the method and the inten sity of agitation and/or aeration on ferrous iron biooxidation. The specific growth rates and the substrate oxidation rate constants in the exponential phase were actually the same (0.069 +/- 0.002 h(-1)), regardle ss of the bioreactor type and the pH condition, if the oxygen transfer rate was higher than approximately 1.0 mg O-2/L/min. The maximum biooxidation c onstants were affected by the oxygen transfer only at lower aeration intens ities. Thus, the oxygen transfer rate could be used as a basis for scaling- up bioreactors for the ferrous iron biooxidation by T. ferrooxidans under a erobic and controlled pH condition.