Biodegradation of Environmentally Hazardous Azo Dyes and Aromatic Amines Using Klebsiella pneumoniae

Abstract

A facultative bacterium was isolated from the sludge of a local dyeing industry for bioremediation of wastewater containing azo dyes. The identified Klebsiella pneumoniae by 16S ribosomal DNA (rDNA) sequence analysis was used for complete degradation of the recalcitrant sulfonated azo dyes in a two-stage process. In Stage I, different azo dyes (monosulfonated, disulfonated, and trisulfonated, 1 mg L−1), were decolorized by more than 95% in less than 24 h. The addition of nicotinamide adenine dinucleotide hydrogen as a redox mediator resulted in faster decolorization of the model azo dye, Methyl Orange. In Stage II, the accumulated 4-aminobenzenesulfonic acid was further degraded under aerobic conditions. Dye degradation products obtained during biodegradation were analyzed by ultraviolet–visible spectroscopy and high-performance liquid chromatography. The phytotoxicity test performed with the dicot seed Cicer arietinum showed that the final degraded products after two-stage sequential process were less toxic. Moreover, the isolated Klebsiella pneumoniae was observed to be efficient compared with the previously reported strains. Thus, the isolated strain has great potential for the degradation of azo dyes and aromatic amines at the source points.