Studies on decolourisation of azo dye Orange G by bacterium isolated from dye contaminated sites

ABSTRACT

In the present study, an azo dye decolourising bacterium, Pseudomonas aeruginosa; JKAK, was isolated and characterised based on morphological, biochemical and 16S rDNA sequence analysis. The strain decolourised 99.12% of 200 mg/L Orange G dye in just 16 h. JKAK also decolourised up to 800 mg/L of the dye by 76.78% in 24 h. The optimum pH and temperature for decolourisation were 8.5 and 40°C, respectively. Also, this strain could decolourise over 90% of the dye in presence of 30 g/L NaCl in less than 20 h. Furthermore, it could decolourise 92.1%, 91.7% and 34.6% of the dye, after 20, 28 and 52 h in the presence of Lead, Zinc and Cobalt ions, respectively. Consortium of JKAK with previously isolated strains of bacteria AK1, AK2 and VKY1 decolourised the dye completely in 12 h. The cell-free extract of JKAK showed azoreductase activity of 0.9 µmoles/min/mg protein. The HPLC and LCMS analysis of the decolourised medium indicated the presence of azo bond breakage products 8-amino-6-hydroxynaphthaline-1,3-disulfonate and aniline. About 42% reduction in phytotoxicity was observed in the decolourised samples. Overall, due to the high decolourising capacity over a wide range of conditions, this strain could be effectively applied for the treatment of textile effluents.

KEYWORDS:

• Pseudomonas aeruginosa
• Orange G
• azo dye
• decolourisation
• azoreductase
• phytotoxicity

Acknowledgments

The authors would like to acknowledge the Department of Biochemistry, Gulbarga University for providing us with the facilities to perform the decolourisation experiments. The authors also thank NCIM, Pune for helping with the identification of the bacterial strain and SAIF-IIT, Bombay for helping with the LCMS analysis.

Disclosure statement

No potential conflict of interest was reported by the author(s).