Kinetics of chromium (VI) reduction by a type strain Shewanella alga under different growth conditions.

We conducted kinetic batch experiments to determine the reduction of Chromium(VI) by a type strain of Shewanella alga (BrY-MT) ATCC 55627. Chromium(VI) was reduced to Chromium(III) by BrY-MT grown in three different substrates: BHIB (brain heart infusion broth), TSB (tryptic soy broth), and M9 (minimum broth). Four different Cr(VI) concentrations 4.836, 10.00, 37.125, and 260.00 mg l-1 were reduced at different rates by BrY-MT in both aerobic and anaerobic conditions. BrY-MT grown in BHIB reduced the maximum amount of Cr(VI) followed by TSB and M9. Carbondioxide produced from bacterial respiration varied with and without Cr(VI) under both aerobic and anaerobic conditions. The Cr(VI) reduction data under anaerobic condition was fitted by a monod model to determine the bacterial kinetic parameters. The kinetic parameters determined by fitting the anaerobic experimental data were used to run a forward simulation for experiments conducted under aerobic conditions. The monod model was modified to account for an inhibition parameter for the Cr(VI) experiment at 260 mg l-1. All the parameters varied within a narrow range, and were distinct for different substrates. Our studies show that, successful in situ bioremediation of Cr(VI) is depended on the type of substrates (electron donors) and the concentration of Cr(VI) in geologic medium.