Decolouration of laboratory dyes by immobilized cells of &lt;i&gt;Pseudomonas aeruginosa&lt;/i&gt; and &lt;i&gt;Bacillus subtilis&lt;/i&gt; at different carbon sources

O B Akpor

doi:10.4314/njb.v34i1.11

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

Highlights

It is estimated that over ten thousand various dyes are prepared all over the world and about 8×105 tons of artificial dyes are used in textile, paper and leather industries globally (Walker and Weatherley, 1997)
Decolouration rate of bromothymol blue was observed to increase from 25.49 % and 18.17 % to 51.49 % and 31.94 %, in presence of the Bacillus subtilis and Pseudomonas aeruginosa immobilized cells
Decolouration rate of bromothymol blue was observed to increase from 25.49 % and 18.17 % to 51.49 % and 31.94 %, in presence of the Bacillus subtilis and Pseudomonas aeruginosa immobilized cells, respectively (Fig. 1)

Summary

Introduction

It is estimated that over ten thousand various dyes are prepared all over the world and about 8×105 tons of artificial dyes are used in textile, paper and leather industries globally (Walker and Weatherley, 1997). A lot of wastewater containing dyes and other pollutants are discharged by these industries. Most of these dyes are not affected by factors like temperature, pH, light and attack from microbes contributing to organic load and toxicity of the wastewater (Nigam et al, 2000). Numerous studies have shown that bacteria can completely degrade and mineralize various dyes under suitable conditions and considering the cost-effectiveness, ease and eco-friendliness of this method in comparison to conventional methods, biological methods of removing dyes from wastewater are very efficient (Kapdan and Erten, 2007; Darwesh et al, 2008; Moawad et al, 2010).

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