Mn(II) oxidation by batch cultures of Pseudomonas putida strain EC112

Manganese(II) oxidation by a new bacterium isolate, Pseudomonas putida strain EC112, was studied in batch reactors over a range of Mn(II) concentrations (1-26 mg/L) in a chemically defined liquid medium (at pH 6.5 and 30°C). Bacterial Mn(II) oxidation initiated after the exponential growth phase and carbon source consumption. The best fit kinetic oxidation parameters of half-saturation coefficient K_s = 1.086 ± 0.029 mg/L and maximum specific substrate utilization rate constant k = 0.180 ± 0.003 mg Mn(II)/(mg dry cell mass · h) were obtained using Monod-type kinetics and fitted with the Levenberg-Marquardt nonlinear least-squared algorithm. Additional experiments assessed the potential of Mn(II) oxidation by strain EC112 in the presence of the oxidation products of humic acid (HA) and manganese dioxide (MnO₂). Results show enhanced biological Mn oxidation and growth. This suggests MnO₂ oxidizes biologically refractory organic matter to substrates that support microorganism growth.