Studies on biological reduction of chromate by Pseudomonas mendocina strain PASS3-P18

Pseudomonas otitidis WL-13, which has a high capacity to decolorize triphenylmethane dyes, was isolated from activated sludge obtained from a wastewater treatment plant of a dyeing industry. This strain exhibited a remarkable color-removal capability when tested against several triphenylmethane dyes under both shaking and static conditions at high concentrations of dyes. More than 95% of Malachite Green and Brilliant Green was removed within 12 h at 500 μol/L dye concentration under shaking conditions. Crystal Violet lost about 13% of its color under the same conditions tested. The rate of decolorization increased when the M9 medium was supplemented with yeast extract. The optimum pH and temperature for color removal were 7–9 and 35–40°C, respectively. The observed changes in the visible spectra and the inspection of bacterial growth indicated the color-removal by the adsorption of dye to the cells during incubation with strains.