Batch experiments were conducted to examine the oxidation of arsenite (As (111)) to arsenate (As (V)) by Alcaligenes faecalis strain 0 1201 isolated from soils. Pure cultures of 01201. completely oxidized As (III) to' As (V) in the exponential growth phase at As (III) concentrations ranging from 10 to 1,000 mg L in less than 12 h. The growth of 01201 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 (111) concentration at 500 mg/L inhibited the growth of 01201, whereas its oxidation product As,(V) did not show any inhibition effects even at concentration as high as 1,000 mg/L. Kinetics studies of As (111) oxidation were performed under the optimal conditions for 01201 at pH 7 and 30 degrees 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 mg/L, maximum reaction rate, coefficient k(mc) of 0.47 mg As (III)/mg dryweight/h, and logistic growth rate coefficient r of 0.22-0.34 h(-1) were obtained using a nonlinear regression analysis.
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