Bioremediation of Some Reactive Dyes Commonly used in Fabric Re-dyeing by Chlorella vulgaris

Aim: The work was aimed at assessing the potential of Chlorella vulgaris in remediation of reactive dyes. Place and Duration of Study: Department of Biological Sciences, Department of Plant Biology and Department of Biochemistry, Bayero University, Kano, Nigeria, between January 2019 and December 2019. Methodology: Wastewater containing individual reactive dyes: reactive red 198 (RR198), reactive yellow 176 (RY176), reactive green 19 (RG19), reactive orange 122 (RO122), reactive red 195 (RR195) and reactive violet 1 (RV1) were collected from a local fabric re-dyeing pit at Kofar Na’isa, Kano, Nigeria. The green microalga C. vulgaris was cultured in Bold Basal medium (BBM) at 30 ± 2°C and subjected to adsorption and decolourization assays of the dyes. Results: The highest dye removal efficiency by enzymatic action was recorded after 48 hours, while that for the biomass adsorption was at day 14, at pH 11.3 and temperature of 30°C. The percentage dye removal by adsorption and decolourization were within the ranges of 68.1-97.8% and 69.8-99.9% respectively. Dye removal decreased with increase in contact time until saturation is attained. Freundlich’s isotherm model was best fitted for the adsorption of the dyes with a strong linear correlation coefficient, R2 ranging from 0.954-0.811. There was a strong linear relationship and high statistical significance among the dyes for both decolourization and adsorption (P value; .01). Conclusion: Chlorella vulgaris was found to be effective in the removal of reactive dyes from textile wastewater samples. The results revealed C. vulgaris to be a cost-effective and eco-friendly biosorbent that can be used for the treatment of wastewaters containing toxic dyes.

Decolorization of Synthetic Azo Dyes under Anaerobic Condition in A Continuous Stirred Tank Reactor

Biological treatment for textile wastewater always has a limitation in term of time of reaction and uncertainty along the process. This study focused on the decolorization of synthetic azo dyes in batch reactors with controlled thermotolerant anaerobic conditions. Less-volatile digested sludge collected from a palm oil biogas reactor was used as the organic biodegradation agent for azo dyes. Digested sludge contains high amounts of microbes with uncertain species viable for decolorization purposes. Sodium acetate trihydrate (C2H9NaO5) was used as carbon source and mixed with a specific composition of minimum salt media (MSM) in batch reactors as an additional nutrient. Digested sludge both in mesophilic (35°C) and thermophilic (55°C) conditions were found to be capable of decolorizing 100, 200 and 300 ppm of three types of azo dyes: Reactive Green 19 (45.56%, 69.73%; 63%, 73.49%; 70.02%, 75.92%), Reactive Orange 16 (46.08%, 78.4%; 64.21%, 85.52%; 74.95%, 85.91%) and Reactive Red 120 (29.11%, 85.32%; 63.35%, 87.69%; 72.02%, 89.5%) respectively after 7 days incubation time. Statistical analysis also showed that the anaerobic thermophilic conditions had significantly accelerated the decolorization process. The anaerobic thermophilic environment will be a good factor to include in future textile wastewater treatment plants.

Adsorption of Reactive Dyes from Aqueous Solution Using Activated Carbon Prepared from Plantain Leaf Sheath Waste

All parts of the plantain are widely used in India for various purposes. But plantain<br /> leaf sheath always ends up as waste material which accumulates as a biowaste. The present study focuses on the preparation of activated carbon using phosphoric acid as activating agent, and its efficacy as an adsorbent for the removal of reactive dyes, Reactive<br /> Green 19, and Reactive Red 141. Batch adsorption studies have been conducted and<br /> optimum adsorption conditions were determined as a function of contact time, initial dye<br /> concentration, adsorbent dosage, and pH. The experimental data were analyzed using<br /> Langmuir, Freundlich and Temkin isotherm models. The pseudo-first and second-order,<br /> intraparticle diffusion, and Elovich models were used to analyze the kinetic parameters<br /> of the adsorption system. Under the optimum conditions (initial dye concentration = 200<br /> mg L–1, adsorbent dose = 1 g, pH = 2, contact time = 220 min for reactive green 19 and<br /> 180 min for reactive red 141), maximum percentage removal for reactive green 19 and<br /> reactive red 141 were obtained as 65.9 % and 72.7 %, respectively. The results demonstrate that activated carbon produced from chemical activation of the plantain waste has the potential of adsorbing reactive dyes from industrial effluents.

Differential Protein Expression in Shewanella seohaensis Decolorizing Azo Dyes

Background:Microbial remediation is an ecologically safe alternative to controlling environmental pollution caused by toxic aromatic compounds including azo dyes. Marine bacteria show excellent potential as agents of bioremediation. However, a lack of understanding of the entailing mechanisms of microbial degradation often restricts its wide-scale and effective application.Objective:To understand the changes in a bacterial proteome profile during azo dye decolorization.Methods:In this study, we tested a Gram-negative bacterium, Shewanella seohaensis NIODMS14 isolated from an estuarine environment and grown in three different azo dyes (Reactive Black 5 (RB5), Reactive Green 19 (RG19) and Reactive Red 120 (RR120)). The unlabeled bacterial protein samples extracted during the process of dye decolorization were subject to mass spectrometry. Relative protein quantification was determined by comparing the resultant MS/MS spectra for each protein.Results:Maximum dye decolorization of 98.31% for RB5, 91.49% for RG19 and 97.07% for RR120 at a concentration of 100 mg L-1 was observed. The liquid chromatography-mass spectrometry - Quadrupole Time of Flight (LCMS-QToF) analysis revealed that as many as 29 proteins were up-regulated by 7 hours of growth and 17 by 24 hours of growth. Notably, these were common across the decolorized solutions of all three azo dyes. In cultures challenged with the azo dyes, the major class of upregulated proteins was cellular oxidoreductases and an alkyl hydroperoxide reductase (SwissProt ID: A9KY42).Conclusion:The findings of this study on the bacterial proteome profiling during the azo dye decolorization process are used to highlight the up-regulation of important proteins that are involved in energy metabolism and oxido-reduction pathways. This has important implications in understanding the mechanism of azo dye decolorization by Shewanella seohaensis.