Arsenite Oxidation by Batch Cultures of Thiomonas Arsenivorans Strain b6

Arsenite [As(III)] oxidation by Thiomonas arsenivorans Strain b6 was investigated in batch reactors at pH 6 and 30 degrees C over As(III) concentrations ranging from 10 to 1,000 mg/L in the absence of added organic carbon. Strain b6 completely oxidized As(III) to arsenate [As(V)] during exponential growth phase for lower levels of As(III) concentrations (< 100 mg/L). At higher levels of 500 and 1,000 mg/L, As(III) oxidation was observed mostly in the exponential phase but continued into the stationary phase of growth. The Haldane substrate inhibition model was used to estimate biokinetic parameters for As(III) oxidation. The best fit parameters of half saturation constant K(s)=33.2 +/- 1.87 mg/L, maximum specific substrate utilization rate k=(0.85 +/- 0.18)-mg As(III)/mg dry cell weight/h, substrate inhibition coefficient K(i)=602.4 +/- 33.6 mg/L, yield coefficient Y=(0.088 +/- 0.0048)-mg cell dry weight/mg As(III), and endogenous decay coefficient k(d)=0.006 +/- 0.002 h(-1) were obtained using the Adams-Bashforth-Moulton algorithm and nonlinear regression technique. Sensitivity analysis revealed that Y and K(i) are the most sensitive to model predictions, while k(d) is the least sensitive to model simulation at both low and high concentrations of As(III).