Arsenite Oxidation by Alcaligenes faecalis Strain O1201

Batch experiments were conducted to examine the oxidation of arsenite (As (III)) to arsenate (As (V)) by Alcaligenes faecalis strain O1201 isolated from soils. Pure cultures of O1201 completely oxidized As (III) to As (V) in the exponential growth phase at As (III) concentrations ranging from 10 to $\mathrm{1,000}\mathrm{mg}∕\mathrm{L}$ in less than 12 h. The growth of O1201 requires an organic substrate as the carbon and energy source, and the oxidation of As (III) was mainly observed in the exponential growth phase. As (III) concentration at $500\mathrm{mg}∕\mathrm{L}$ inhibited the growth of O1201, whereas its oxidation product As (V) did not show any inhibition effects even at concentration as high as $\mathrm{1,000}\mathrm{mg}∕\mathrm{L}$ . Kinetics studies of As (III) oxidation were performed under the optimal conditions for O1201 at pH 7 and 30°C in a chemical defined medium with citrate as the sole carbon source. The Monod expression coupled with a logistic growth model was used to analyze the kinetics of As (III) oxidation. The best fit parameters of half-velocity coefficient $K_c$ of $15\mathrm{mg}∕\mathrm{L}$ , maximum reaction rate coefficient $k_{\mathrm{mc}}$ of 0.47 mg As $\left(\mathrm{III}\right)∕\mathrm{mg}$ dry weight/h, and logistic growth rate coefficient $r$ of $0.22\text{–}0.34{\mathrm{h}}^{-1}$ were obtained using a nonlinear regression analysis.