Notice of RetractionMicrobial Degradation of Chromium Azo Dye

Notice of Retraction

After careful and considered review of the content of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE\´s Publication Principles.

We hereby retract the content of this paper. Reasonable effort should be made to remove all past references to this paper.

The presenting author of this paper has the option to appeal this decision by contacting TPII@ieee.org.

A bacterium, Pseudomonas fluorescens, capable to degrade a model chromium azo dye, Acid Yellow 99 (AY99), at the highest efficiency, was isolated from a sludge sample collected from a dyeing factory in Huizhou, China. The optimal conditions of decolorization of AY99 were determined by "response surface method". Under the optimized conditions for decolorizing (0.48 g/L cell dry weight, 0.51 g/L (NH₄)₂SO₄ and pH = 7.30), the bacterium decolorized 95.7+0.4% of dye. The cells of Ps. fluorescens were immobilized by PVA to build a laboratory scale (1 L) bioreactor. 500 mL synthetic AY99 solution was treated by 201.6 g PVA gel cubes containing 320 mg of bacterial cells. Performance of this bioreactor was evaluated as decolorization (%) efficiency, change of total organic carbon (TOC) content, the Microtox^® EC₅₀ test and total dissolved chromium. Besides that, 5 consecutive runs were conducted to evaluate the performance stability of the treatment system. The activity of immobilized cells was stable since the decolorization efficiency had no significant different in the 5 consecutive runs. Lastly, the intermediate(s)/product(s) generated during degradation were subjected to Fourier transform-infrared spectroscopic analysis to detect various functional groups. The results indicated the presence of Cr(III) complexed compounds.