Decolouration of laboratory dyes by immobilized cells of <i>Pseudomonas aeruginosa</i> and <i>Bacillus subtilis</i> at different carbon sources

Abstract

Dyes are indicated as one of the most problematic compounds in industrial effluents. This is due to their high solubility and low degradability. The aim of the study was to evaluate the effect of external carbon source on decolouration of bromothymol blue, crystal violet and methylene blue by alginate immobilized cells of Bacillus subtilis and Pseudomonas aeruginosa. A total of five carbon sources (fructose, sucrose, glucose, methanol, lactose and sodium acetate) were used for the study. The study revealed highest decolouration of the bromothymol blue occurring in media that contained sodium acetate as external carbon source. Decolouration rate of bromothymol blue was observed to increase from 25.49 % and 18.17 % (at 24 h incubation) to 51.49 % and 31.94 % (at 144 h incubation), in presence of the Bacillus subtilis and Pseudomonas aeruginosa immobilized cells. For decolouration of the crystal violet, glucose and sodium acetate were observed to be the most appropriate carbon sources. With glucose as carbon source in the media, decolouration rates of 57.48 % and 41.23 % at the end of incubation were observed for the crystal violet dyes in presence of the Bacillus subtilis and Pseudomonas aeruginosa cells, respectively. None of the carbon sources used for the investigation was found to enhance decolouration of the methylene blue by the test bacteria species. The study revealed the possible application of the immobilized cells in scale up studies for the remediation of textile effluents.

Keywords: Decolouration,Dye,Immobilizedbacteria,Wastewater