The objective of this study was to evaluate a direct classical bioengineering approach to model data generated from continuous bio-oxidation of Fe2+ by a Leptospirillum ferrooxidans-dominated culture fed with either 9 g or 18 g Fe2+L-1 under chemostat conditions (dilution rates were between 0.051 and 0.094 h(-1)). The basic Monod and Pirt equations have successfully been integrated in an overall mass balance procedure, which has not been previously presented in this detail for Fe2+ oxidation. To ensure chemostat conditions, it was found that the range of the dilution rates had to be limited. A too long retention time might cause starvation or non-negligible death rate whereas, a too short retention time may cause a significant alteration in solution chemistry and culture composition. Modeling of the experimental data suggested that the kinetic- and yield parameters changed with the overall solution composition. However, for respective feed solutions only minor changes of ionic strength and chemical speciation can be expected within the studied range of dilution rates, which was confirmed by thermodynamic calculations and conductivity measurements. The presented model also suggests that the apparent Fe3+ inhibition on specific Fe2+ utilization rate was a direct consequence of the declining biomass yield on Fe2+ due to growth uncoupled Fe2+ oxidation when the dilution rate was decreased. The model suggested that the maintenance activities contributed up to 90% of the maximum specific Fe2+ utilization rate, which appears close to the critical dilution rate.