Evaluation of Bacillus sp. MZS10 for decolorizing Azure B dye and its decolorization mechanism

Contamination of textile dyes in aquatic environment: Adverse impacts on aquatic ecosystem and human health, and its management using bioremediation

Textile dyes are the burgeoning environmental contaminants across the world. They might be directly disposed of from textile industries into the aquatic bodies, which act as the direct source for the entire ecosystem, ultimately impacting the human beings. Hence, it is essential to dissect the potential adverse outcomes of textile dye exposure on aquatic plants, aquatic fauna, terrestrial entities, and humans. Analysis of appropriate literature has revealed that textile dye effluents could affect the aquatic biota by disrupting their growth and reproduction. Various aquatic organisms are targeted by textile dye effluents. In such organisms, these chemicals affect their development, behavior, and induce oxidative stress. General populations of humans are exposed to textile dyes via the food chain and drinking contaminated water. In humans, textile dyes are biotransformed into electrophilic intermediates and aromatic amines by the enzymes of the cytochrome family. Textile dyes and their biotransformed products form the DNA and protein adducts at sub-cellular moiety. Moreover, these compounds catalyze the production of free radicals and oxidative stress, and trigger the apoptotic cascades to produce lesions in multiple organs. In addition, textile dyes modulate epigenetic factors like DNA methyltransferase and histone deacetylase to promote carcinogenesis. Several bioremediation approaches involving algae, fungi, bacteria, biomembrane filtration techniques, etc., have been tested and some other hybrid systems are currently under investigation to treat textile dye effluents. However, many such approaches are at the trial stage and require further research to develop more efficient, cost-effective, and easy-to-handle techniques.

Synergistic degradation of Azure B and sulfanilamide antibiotics by the white-rot fungus Trametes versicolor with an activated ligninolytic enzyme system

The treatment of complex polluted wastewater has become an increasingly critical concern for the various types of hazardous organic compounds, including synthetic dyes and pharmaceuticals. Due to their efficient and eco-friendly advantages, the white-rot fungi (WRF) have been applied to degrade environmental pollutants. This study aimed to investigate the removal ability of WRF (i.e., Trametes versicolor WH21) in the co-contamination system composed of Azure B dye and sulfacetamide (SCT). Our study discovered that the decolorization of Azure B (300 mg/L) by strain WH21 was significantly improved (from 30.5% to 86.5%) by the addition of SCT (30 mg/L), while the degradation of SCT was also increased from 76.4% to 96.2% in the co-contamination system. Transcriptomic and biochemical analyses indicated that the ligninolytic enzyme system was activated by the enhanced enzymatic activities of MnPs and laccases, generating higher concentration of extracellular H₂O₂ and organic acids in strain WH21 in response to SCT stress. Purified MnP and laccase of strain WH21 were revealed with remarkable degradation effect on both Azure B and SCT. These findings significantly expanded the existing knowledge on the biological treatment of organic pollutants, indicating the strong promise of WRF in the treatment of complex polluted wastewater.

Whole cell of pure Clostridium butyricum CBT-1 from anaerobic bioreactor effectively hydrolyzes agro-food waste into biohydrogen

Recycling organic waste and converting them into renewable energy are a promising route for environment protection and effective biochemical reactions suitable for industrial hydrogen synthesis. This study targeted to isolate a pure anaerobic culture with potential to hydrolyze different biomass and production of biohydrogen. For this, a sample of full-scale anaerobic digester, fed with a multicomponent solid, was inoculated on Reinforced Clostridial Medium (RCM) in strict anaerobic conditions. An anaerobic Clostridium butyricum CBT-1 strain was isolated, identified from morphological and 16S rRNA sequence. The CBT-1 culture expressed amylase, cellulase and peroxidases activities. The strain exhibited visual decolorization of both Azure B and crystal violet dyes. In batch fermentation experiment, the CBT-1 produced highest of 3.06, 2.67 and 2.46 mol/mol H₂ yield from glucose, starch and cellulose respectively, whereas, the CBT-1 showed low 0.43 mol H₂/mol of substrate from untreated rice straw due to lignin in compact structure and comparatively high H₂ yield of 1.91 and 2.01 mol H₂/mol of substrate rice straw hydrolysate and kitchen food waste (KFWS) respectively. The cumulative volumetric yield of H₂ was 358.15, 300.8 and 294.5NmL/gSub from glucose, starch and cellulose respectively. Similarly, the cumulative H₂ volume was 76.7, 184.4, 237.2 NmL/gVS from untreated rice straw, rice straw hydrolysate and kitchen food waste. This study emphasizes the prospects to find similar robust anaerobic culture for hydrolyzing complex biomass. Such strains could be used as standard co-inoculum for biohydrogen obtaining and as the biocatalyst for commercial scale applications.

A critical review on the treatment of dye-containing wastewater: Ecotoxicological and health concerns of textile dyes and possible remediation approaches for environmental safety

The synthetic dyes used in the textile industry pollute a large amount of water. Textile dyes do not bind tightly to the fabric and are discharged as effluent into the aquatic environment. As a result, the continuous discharge of wastewater from a large number of textile industries without prior treatment has significant negative consequences on the environment and human health. Textile dyes contaminate aquatic habitats and have the potential to be toxic to aquatic organisms, which may enter the food chain. This review will discuss the effects of textile dyes on water bodies, aquatic flora, and human health. Textile dyes degrade the esthetic quality of bodies of water by increasing biochemical and chemical oxygen demand, impairing photosynthesis, inhibiting plant growth, entering the food chain, providing recalcitrance and bioaccumulation, and potentially promoting toxicity, mutagenicity, and carcinogenicity. Therefore, dye-containing wastewater should be effectively treated using eco-friendly technologies to avoid negative effects on the environment, human health, and natural water resources. This review compares the most recent technologies which are commonly used to remove dye from textile wastewater, with a focus on the advantages and drawbacks of these various approaches. This review is expected to spark great interest among the research community who wish to combat the widespread risk of toxic organic pollutants generated by the textile industries.

The effect of Ralstonia pickettii bacterium addition on methylene blue dye biodecolorization by brown-rot fungus Daedalea dickinsii

Methylene blue (MB) is one of synthetic dyes that is used in the textile industry which is difficult to degrade in nature. Previously, the brown-rot fungus (BRF) Daedalea dickinsii had shown a good ability to degrade MB, however, the decolorization ability was relatively still low and had a long period of incubation. Therefore, improvement of process is needed to increase the ability of D. dickinsii to decolorize MB. In this study, the effect of Ralstonia pickettii bacterium addition on MB biodecolorization by the BRF D. dickinsii in potato dextrose broth (PDB) medium was investigated. The amount of R. picketti that was added to the culture of D. dickinsii were 2, 4, 6, 8, and 10 mL (1 mL ≈ 1.39 × 10⁸ CFU). The cultures had ability to decolorize MB (100 mg/L) at 30 °C after 7 days incubation. The highest percentage of MB biodecolorization was obtained at addition of 10 mL of R. pickettii approximately 89%, while biodecolorization process by particularly D. dickinsii was approximately 17%. The MB degradation metabolites by mixed cultures of D. dickinsii and 10 mL of R. pickettii were Azure A, thionine, glucose-MB, C₁₂H₁₁N₃SO₆ and C₁₂H₁₃N₃O₆. This study indicated that the addition of R. pickettii could enhance MB biodecolorization by fungus D. dickinsii. Besides that, this study also indicated that mixed cultures of D. dickinsii and R. pickettii has great potential for high efficiency, fast and cheap dye wastewater treatment.

A critical review on advances in the practices and perspectives for the treatment of dye industry wastewater

Rapid industrialization has provided comforts to mankind but has also impacted the environment harmfully. There has been severe increase in the pollution due to several industries, in particular due to dye industry, which generate huge quantities of wastewater containing hazardous chemicals. Although tremendous developments have taken place for the treatment and management of such wastewater through chemical or biological processes, there is an emerging shift in the approach, with focus shifting on resource recovery from such wastewater and also their management in sustainable manner. This review article aims to present and discuss the most advanced and state-of-art technical and scientific developments about the treatment of dye industry wastewater, which include advanced oxidation process, membrane filtration technique, microbial technologies, bio-electrochemical degradation, photocatalytic degradation, etc. Among these technologies, microbial degradation seems highly promising for resource recovery and sustainability and has been discussed in detail as a promising approach. This paper also covers the challenges and future perspectives in this field.

Biodegradation of Azure-B dye by Serratia liquefaciens and its validation by phytotoxicity, genotoxicity and cytotoxicity studies

The azo dyes in textile industry are a major source of environmental pollution and cause serious threat to aquatic flora and fauna. The present study aims to evaluate the potential of previously isolated lignin peroxidase (LiP) enzyme producing Serratia liquefaciens in degradation of Azure-B (AB) dye. S. liquefaciens showed rapid decolourisation of AB dye (100 mg L^-1) in mineral salt medium (MSM) supplemented with 0.2% glucose and yeast extract, and more than 90% dye decolourisation was observed at 48 h when incubated at 30 °C. Decolourisation conditions were optimized by Response Surface Methodology (RSM) using Box-Behnken Designs (BBD). The dye degradation was further confirmed by ATR-FTIR and GC-MS analysis. Toxicological studies of untreated (UT) and bacterial treated (BT) AB dye solutions were studied by using phytotoxicity, genotoxicity and cytotoxicity endpoints. Phytotoxicity assay using Vigna radiata indicated that bacterial treatment led to detoxification of AB dye. Genotoxicity assay with Allium cepa showed that pure AB dye solutions significantly reduced mitotic index (MI) and induced various chromosomal abnormalities (CAs) like c-mitosis, stickiness, chromosome break, anaphase bridges, vagrant chromosomes and binucleated and micronucleated cell in the root tip cells, whereas, bacterial treated solutions induced relatively less genotoxicity in nature. Improved cell survivability (%) was also noted in kidney cell line (NRK-52E) after S. liquefaciens treated dye solutions than the pure dye solutions. The findings suggest that S. liquefaciens could be a potential bacterium for azo dye degradation, as it is effective in lowering of toxic effects of AB dye.

The ability of brown-rot fungus Daedalea dickinsii to decolorize and transform methylene blue dye

The ability of Daedalea dickinsii to decolorize and transform methylene blue (MB) dye was investigated. MB was decolorized in potato dextrose agar medium after adding MB at concentrations of 50, 75, and 100 mg L^-1. D. dickinsii decolorized MB with decolorization index values of 0.92, 0.90, and 0.88 at MB concentrations of 50, 75, and 100 mg L^-1, respectively. The 100 mg L¹ MB concentration was selected for biotransformation in liquid potato dextrose broth medium. D. dickinsii transformed approximately 54% of the MB after a 14-day incubation. 3-(Dimethylamino)-7-(methylamino) phenothiazine (C₁₅H₁₆N₃S), 3,7-bis(dimethylamino)-4aH-phenothiazin-5-one (C₁₆H₁₉N₃SO), and 4-(dimethylamino)-2-[m(dimethylamino) phenylsulfinyl] benzenamine (C₁₆H₂₁N₃SO) were detected as MB metabolic products. This is the first report of MB transformation by the brown-rot fungi D. dickinsii. These results indicate that D. dickinsii can be used to decolorize and biotransform MB dye.

Evaluation of bioremediation potentiality of ligninolytic Serratia liquefaciens for detoxification of pulp and paper mill effluent

Due to high pollution load and colour contributing substances, pulp and paper mill effluents cause serious aquatic and soil pollution. A lignin-degrading bacterial strain capable of decolourising Azure-B dye was identified as lignin peroxidase (LiP) producing strain LD-5. The strain was isolated from pulp and paper mill effluent contaminated site. Biochemical and 16S rDNA gene sequence analysis suggested that strain LD-5 belonged to the Serratia liquefaciens. The strain LD-5 effectively reduced pollution parameters (colour 72%, lignin 58%, COD 85% and phenol 95%) of real effluent after 144h of treatment at 30°C, pH 7.6 and 120rpm. Extracellular LiP produced by S. liquefaciens during effluent decolourisation was purified to homogeneity using ammonium sulfate (AMS) precipitation and DEAE cellulose column chromatography. The molecular weight of the purified lignin peroxidase was estimated to be ∼28kDa. Optimum pH and temperature for purified lignin peroxidase activity were determined as pH 6.0 and 40°C, respectively. Detoxified effluent was evaluated for residual toxicity by alkaline single cell (comet) gel electrophoresis (SCGE) assay using Saccharomyces cerevisiae MTCC 36 as model organism. The toxicity reduction to treated effluent was 49.4%. These findings suggest significant potential of S. liquefaciens for bioremediation of pulp and paper mill effluent.

Enhanced bioconversion of ethylene glycol to glycolic acid by a newly isolated Burkholderia sp. EG13

Burkholderia sp. EG13 with high ethylene glycol-oxidizing activity was isolated from soil, which could be used for the synthesis of glycolic acid from the oxidation of ethylene glycol. Using the resting cells of Burkholderia sp. EG13 as biocatalysts, the optimum reaction temperature and pH were 30 °C and 6.0, respectively. After 24 h of biotransformation, the yield of glycolic acid from 200 mM ethylene glycol was 98.8 %. Furthermore, an integrated bioprocess for the production of glycolic acid which involved in situ product removal (ISPR) was investigated. Using fed-batch method with ISPR, a total of 793 mM glycolic acid has been accumulated in the reaction mixture after the 4th feed.