Decolorization and biodegradation of methyl red by Klebsiella pneumoniae RS-13

Bacterial strains isolated from dye-contaminated sludge decolorized a toxic azo dye, namely, methyl red (MR). Klebsiella pneumoniae RS-13 was selected because of its better abilities to completely decolorize and degrade MR under aerobic conditions. Effects of physico-chemical parameters, such as: temperature and aeration, concentrations of glucose, ethanol, ammonium sulfate and pH of the culture medium on the MR degradation by the bacterium and a previously isolated aerobic MR-degrading bacterium, Acetobacter liquefaciens S-1, were determined. K. pneumoniae RS-13 had higher MR degradation ability than A. liquefaciens S-1. Under optimal conditions, K. pneumoniae RS-13 completely decolorized and degraded 100 mg l −1 of MR in cultural medium. The high MR degradation ability and low nutrient and environmental requirements of K. pneumoniae RS-13 enable this bacterium to be used in the treatment of industrial effluent containing azo dyes.