Assessment of hepatotoxicity and nephrotoxicity in Cirrhinus mrigala induced by trypan blue - An azo dye

Biotransformation of the azo dye reactive orange 16 by Aspergillus flavus A5P1: Performance, genetic background, pathway, and mechanism

This study reports the strain Aspergillus flavus A5P1 (A5P1), which is with the capable of degrading the azo dye reactive orange 16 (RO16). The mechanism of RO16 degradation by A5P1 was elucidated through genomic analysis, enzymatic analysis, degradation pathway analysis and oxidative stress analysis. Strain A5P1 exhibited aerobic degradation of RO16, with optimal degradation at an initial pH of 3.0. Genomic analysis indicates that strain A5P1 possesses the potential for acid tolerance and degradation of azo dye. Enzymatic analysis, combined with degradation product analysis, demonstrated that extracellular laccase, intracellular lignin peroxidase, and intracellular quinone reductase were likely key enzymes in the RO16 degradation process. Oxidative stress analysis revealed that cell stress responses may participate in the RO16 biotransformation process. The results indicated that the biotransformation of RO16 may involves biological processes such as transmembrane transport of RO16, cometabolism of the strain with RO16, and cell stress responses. These findings shed light on the biodegradation of RO16 by A5P1, indicating A5P1's potential for environmental remediation.

Biochar obtained from alkaline earth metal-treated mushroom residue: Thermal behavior and methyl orange adsorption capability

To achieve the resource utilization of edible fungi residue and obtain efficient adsorbents for treating dyeing wastewater, biochars were prepared from mushroom residue (MR) with the introduction of alkaline-earth metals (AEMs) and used for methyl orange (MO) wastewater treatment. The thermal behavior of the AEM-treated MR was analyzed using thermogravimetric analysis. The physicochemical properties of the biochars obtained from AEM-treated MR (MRCs) were characterized using Fourier transform infrared spectroscopy, laser particle size analyzer, N2 adsorption/desorption, and scanning electron microscopy. The adsorption performance of MRCs on MO was also investigated. The involvement of AEMs was found to obviously move the main pyrolysis zone of MR to a low temperature region and reduce the temperature corresponding to the maximum weight loss rate and activation energy, which is highly dependent on the concentration of AEMs, the anion and cationic species of the AEMs. Moreover, the addition of AEMs resulted in a decrease in oxygen-containing functional groups (-OH, CO, or C-O), a weakening of surface negative charges, an enhancement in aromatic functional groups, and an increase in specific surface area of the MRCs. The adsorption performance of MO on MRCs was significantly improved with the introduction of AEMs as well. Among them, MR pre-treated with 5 mmol/g MgCl2 (MR-MgCl2-5) shows the lowest temperature corresponding to the maximum weight loss rate and the lowest activation energy of 278.52 °C and 4.28 kJ/mol, respectively. The biochar prepared from MR-MgCl2-5 under 400 °C (MR-MgCl2-5-400C) has the weakest surface negative charge and the highest adsorption capacity for MO. The adsorption isotherms, adsorption kinetics, and thermodynamic analysis results showed that the adsorption of MO on MR-MgCl2-5-400C was a spontaneous, chemically dominant monolayer adsorption, with a theoretical maximum adsorption capacity of 81.30 mg/g. This study suggests that AEMs treatment, especially with 5 mmol/g MgCl2, can readily transform edible fungi residue into a low-cost, high-efficient dyeing wastewater adsorbent.

Systematic computational toxicity analysis of the ozonolytic degraded compounds of azo dyes: Quantitative structure-activity relationship (QSAR) and adverse outcome pathway (AOP) based approach

The present study identifies and analyses the degraded products of three azo dyes (Reactive Orange 16, Reactive Red 120, and Direct Red 80) and proffers their in silico toxicity predictions. In our previously published work, the synthetic dye effluents were degraded using an ozonolysis-based Advanced Oxidation Process. In the present study, the degraded products of the three dyes were analysed using GC-MS at endpoint strategy and further subjected to in silico toxicity analysis using Toxicity Estimation Software Tool (TEST), Prediction Of TOXicity of chemicals (ProTox-II), and Estimation Programs Interface Suite (EPI Suite). Several physiological toxicity endpoints, such as hepatotoxicity, carcinogenicity, mutagenicity, cellular and molecular interactions, were considered to assess the Quantitative Structure-Activity Relationships (QSAR) and adverse outcome pathways. The environmental fate of the by-products in terms of their biodegradability and possible bioaccumulation was also assessed. Results of ProTox-II suggested that the azo dye degradation products are carcinogenic, immunotoxic, and cytotoxic and displayed toxicity towards Androgen Receptor and Mitochondrial Membrane Potential. TEST results predicted LC50 and IGC50 values for three organisms Tetrahymena pyriformis, Daphnia magna, and Pimephales promelas. EPISUITE software via the BCFBAF module surmises that the degradation products' bioaccumulation (BAF) and bioconcentration factors (BCF) are high. The cumulative inference of the results suggests that most degradation by-products are toxic and need further remediation strategies. The study aims to complement existing tests to predict toxicity and prioritise the elimination/reduction of harmful degradation products of primary treatment procedures. The novelty of this study is that it streamlines in silico approaches to predict the nature of toxicity of degradation by-products of toxic industrial affluents like azo dyes. These approaches can assist the first phase of toxicology assessments for any pollutant for regulatory decision-making bodies to chalk out appropriate action plans for their remediation.

Anaerobic Membrane Bioreactor (AnMBR) for the Removal of Dyes from Water and Wastewater: Progress, Challenges, and Future Perspectives

The presence of dyes in aquatic environments can have harmful effects on aquatic life, including inhibiting photosynthesis, decreasing dissolved oxygen levels, and altering the behavior and reproductive patterns of aquatic organisms. In the initial phase of this review study, our aim was to examine the categories and properties of dyes as well as the impact of their toxicity on aquatic environments. Azo, phthalocyanine, and xanthene are among the most frequently utilized dyes, almost 70–80% of used dyes, in industrial processes and have been identified as some of the most commonly occurring dyes in water bodies. Apart from that, the toxicity effects of dyes on aquatic ecosystems were discussed. Toxicity testing relies heavily on two key measures: the LC50 (half-lethal concentration) and EC50 (half-maximal effective concentration). In a recent study, microalgae exposed to Congo Red displayed a minimum EC50 of 4.8 mg/L, while fish exposed to Disperse Yellow 7 exhibited a minimum LC50 of 0.01 mg/L. Anaerobic membrane bioreactors (AnMBRs) are a promising method for removing dyes from water bodies. In the second stage of the study, the effectiveness of different AnMBRs in removing dyes was evaluated. Hybrid AnMBRs and AnMBRs with innovative designs have shown the capacity to eliminate dyes completely, reaching up to 100%. Proteobacteria, Firmicutes, and Bacteroidetes were found to be the dominant bacterial phyla in AnMBRs applied for dye treatment. However, fouling has been identified as a significant drawback of AnMBRs, and innovative designs and techniques are required to address this issue in the future.