Science Letters

Effect of light on the biodegradation of selective azo dyes by Escherichia coli and Pseudomonas sp. and optimization of conditions for decolorization

Muhammad Kashif, Abdul Jabbar, Abdul Ghaffar*, Muhammad Yameen, Bushra Munir

Department of Applied Chemistry and Biochemistry, Government College University, Faisalabad, 38000, Pakistan

Abstract

The degradation of two azo dyes; congo red and acid red 27, commonly used in textile industries, was investigated using Pseudomonas sp. and Escherichia coli strains isolated from dye contaminated soil sludge. An aqueous medium containing 100 mg/L of dyes were used for the biodegradation experiments. The degradation results as color removal performance were obtained after 5 days incubation. Different factors like azoreductases specificity, pH and effects of a range of wavelengths of light on decolorization efficiencies were studied. Pseudomonas sp. showed highest degradation rate for congo red and Escherichia coli showed highest degradation rate for acid red 27. The color of congo red and acid red 27 dyes were removed up to 98% and 99%, respectively by Pseudomonas sp. and E. coli at the end of anaerobic incubation. Neutral pH was found to be the most appropriate and presence of light showed enhancement of biodegradation rate. Shorting of wavelength of light increased the rate of degradation. Irradiation of UV light before the introduction of microbial strains showed complete color removal only in 2 days period. UV/Visible spectrophotometer was used to monitor the decolorization process.

Keywords: Azo dyes; congo red; acid red 27; Escherichia coli; Pseudomonas sp.; Photo-biodegradation.

Received December 12, 2013; Revised February 21, 2014; Accepted February 27, 2014

*Corresponding Author: Abdul Gaffar; Email: aghaffaruaf@yahoo.com