The ferrous iron oxidation kinetics of Thiobacillus ferrooxidans in batch cultures |
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Authors: | M Boon C Ras J J Heijnen |
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Institution: | (1) Department of Biochemical Engineering, Kluyver Laboratory of Biotechnology, Julianalaan 67, 2628 BC Delft, The Netherlands e-mail: M.Boon@stm.tudelft.nl Tel.: +31-15-2781551 Fax: +31-15-2782355, NL |
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Abstract: | The ferrous iron oxidation kinetics of Thiobacillus ferrooxidans in batch cultures was examined, using on-line off-gas analyses to measure the oxygen and carbon dioxide consumption rates
continuously. A cell suspension from continuous cultures at steady state was used as the inoculum. It was observed that a
dynamic phase occurred in the initial phase of the experiment. In this phase the bacterial ferrous iron oxidation and growth
were uncoupled. After about 16 h the bacteria were adapted and achieved a pseudo-steady state, in which the specific growth
rate and oxygen consumption rate were coupled and their relationship was described by the Pirt equation. In pseudo-steady
state, the growth and oxidation kinetics were accurately described by the rate equation for competitive product inhibition.
Bacterial substrate consumption is regarded as the primary process, which is described by the equation for competitive product
inhibition. Subsequently the kinetic equation for the specific growth rate, μ, is derived by applying the Pirt equation for bacterial substrate consumption and growth. The maximum specific growth rate,
μ
max, measured in the batch culture agrees with the dilution rate at which washout occurs in continuous cultures. The maximum
oxygen consumption rate, q
O2,max, of the cell suspension in the batch culture was determined by respiration measurements in a biological oxygen monitor at
excess ferrous iron, and showed changes of up to 20% during the course of the experiment. The kinetic constants determined
in the batch culture slightly differ from those in continuous cultures, such that, at equal ferric to ferrous iron concentration
ratios, biomass-specific rates are up to 1.3 times higher in continuous cultures.
Received: 8 February 1999 / Accepted: 17 February 1999 |
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