Growth of textile industries led to production of enormous dye varieties. These textile dyes are largely used, chemically stable and easy to synthesize. But they are recalcitrant and persist as less biodegradable pollutants when discharged into waterbodies. Potential use of enzyme-linked bioremediation of textile dyes will control their toxicity in waterbodies. Bioinformatics and Molecular docking tool provides an insight into remediation mechanism by predicting susceptibility of dye degradation using oxidoreductive enzymes. In this study, six dyes, Reactive Red F3B, Remazol Red RGB, Joyfix Red RB, Joyfix Yellow MR, Remazol Blue RGB and Turquoise CL-5B of azo, anthraquinone and phthalocyanine molecular class were identified as potential targets for degradation by laccase and azoreductase of Aeromonas hydrophila in addition to Lysinibacillus sphaericus through in silico docking tool BioSolveIT-FlexX. Azoreductase breaks azo bonds by ping-pong mechanism whereas laccase decolorizes dyes by free radical mechanism which is not specific in nature. Results were analyzed based on parameters like stability, catalytic action and selectivity for enzyme-dye interactions. Amino acids of enzymes interacted with several dyes substantiating variations in active site for enzyme-ligand binding affinity. This suggests the role of enzymes in decolorizing an extensive variety of textile dyes, thereby, aiding in understanding the enzyme mechanisms in Bioremediation.

Polycyclic aromatic hydrocarbons (PAHs) are one of the most common contaminants in soil. Arbuscular mycorrhizal (AM) fungi make host plants resistant to pollutants. This study aims to evaluate the impact of anthracene, phenanthrene and dibenzothiophene on the AM fungus Rhizophagus custos, isolated from soil contaminated by heavy metals and PAHs, under monoxenic conditions. We found a high level of tolerance in R. custos to the presence of PAHs, especially in the case of anthracene, in which no negative effect on AM-colonized root dry weight (root yield) was observed, and also a decrease in the formation of anthraquinone was detected. Increased PAH dissipation in the mycorrhizal root culture medium was observed; however, dissipation was affected by the level of concentration and the specific PAH, which lead us to a better understanding of the possible contribution of AM fungi, and in particular R. custos, to pollutant removal.

Thirty-two surface sediment samples, collected from the Taiwan Strait (TWS), were investigated for the occurrence, composition profile, and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs). PAHs were ubiquity in the TWS with a total concentration (∑PAHs, excluding naphthalene due to its high volatility) ranging from 17.8–213 ng g⁻¹. Benzo[b] fluoranthene, fluoranthene, phenanthrene, and pyrene were the predominant PAHs. Also, eight OPAHs were detected, having a cumulative concentration range (∑OPAHs) of 10.5–118 ng g⁻¹, predominated by anthraquinone and 6H-Benzo[c,d]Pyren-6-one. Higher concentrations of ∑PAHs and ∑OPAHs were detected at sampling sites adjacent to the mainland and in the northwest part of the TWS. The results suggested important continental input, and particle sedimentation under the specific hydrodynamic conditions of the region. Based on the measured concentrations and sediment quality guidelines, PAHs had a limited ecological impact on the area.

A novel heavy metal resistant actinobacterial strain was isolated from an old lead and zinc mine in north-eastern Algeria. This strain was shown to resist high concentrations of heavy metals, including up to 500 ppm arsenic, 700 ppm cadmium, 1750 ppm chromium, 1250 ppm cobalt, 1000 ppm copper, 2750 ppm iron, 2750 ppm lead, 800 ppm mercury, 1750 ppm nickel, and 2750 ppm zinc. In addition, it was able to degrade dyes of the most used families, i.e., triphenylmethane (Malachite Green), azo (Ponceau S), and anthraquinone (Remazol Brilliant Blue R) dyes at 97.79%, 62.93%, and 39.41%, respectively. This bacterium was identified by sequencing the 16S rRNA encoding gene and affiliated to the genus Streptomyces by the RDP Naive Bayesian rDNA Classifier Version 2.11. The genome of Streptomyces sp. KY75 was sequenced using Illumina MiSeq and Oxford Nanopore. It was annotated by the MicroScope platform, and gene codings for resistance to heavy metals and dye biodecolorization were identified. It has a single linear chromosome with 7,837,660 bp and a GC content of 71.58%, 7509 of coding sequences (CDS), 66 tRNA genes, 18 rRNA genes, and 11 pseudogenes. The effect of hexavalent chromium on the dye biodegradation in liquid medium was also tested. Surprisingly, the dye biodegradation was not affected by the addition of hexavalent chromium. These observations make the actinobacterial strain Streptomyces sp. KY75 a good candidate for the bioremediation of textile dyeing industry effluents.

The present study focused on the full valorization of the tomato by-product, also known as tomato pomace consisting mainly of tomato peels and tomato seeds, by recovering natural antioxidants and edible oil, and subsequently reutilizing the leftover solid residues for the production of low-cost biosorbent. The tomato peel extract recovered using ethanol as food-grade solvent contained high phenol and flavonoid contents (199.35 ± 0.35-mg gallic acid equivalents (GAE)/g and 102.10 ± 0.03-mg quercetin equivalent (QE)/g, respectively). Even its lower content of lycopene (3.67 ± 0.04 mg/100 g), tomato peel extract showed potent antioxidant activity and can be therefore used as natural antioxidants either for food or cosmetic applications. High nutritional quality edible oil (17.15%) was extracted from tomato seeds and showed richness in unsaturated fatty acids (74.62%), with linoleic acid being the most abundant polyunsaturated fatty acid (49.70%). After recovery of these valuable compounds, the extraction solid leftovers were used to produce low-cost biosorbent tested for dye removal. Results showed that the highest biosorption yields were increasingly attributed to the acidic, direct, anthraquinone, then reactive dyes. Overall, the obtained results strongly support the complete utilization of tomato pomace for the recovery of valuable compounds and the sequential production of low-cost biosorbent.

The practical applicability of decolorization techniques for synthetic textile wastewater (STW) mimicking real conditions in terms of organic matter and carbonate alkalinity content remains unclear. To address this issue, this study investigated the decolorization of an anthraquinone dye, Acid Blue 25 (AB-25), in STW using advanced oxidation processes (AOPs). The oxidation kinetics of AB-25 in STW and ultra-pure water (UPW) under UV-H₂O₂ and UV-TiO₂ were comparatively studied. In UPW, the first-order rate constant with UV-TiO₂ (0.5 g/L; k: 2.79 × 10⁻² 1/min) was more than twice that with UV-H₂O₂ (100 mg/L; k: 1.14 × 10⁻² 1/min), corresponding to 85% and 72% decolorization, respectively. Interestingly, in STW, the decolorization was slightly higher with UV-H₂O₂ than with UV-TiO₂; at neutral pH, the first-order rate constants were 2.1 × 10⁻³ 1/min and 1.8 × 10⁻³ 1/min, accounting for 29% and 21% decolorization, respectively. This behavior can be attributed to the influence of background constituents, especially alkaline components (carbonate, bicarbonate). The combined influence of alkalinity and pH accounted for ~ 45%. For practical application, these results suggest that pH should be kept under 4.5 to ensure feasible treatment of STW via AOPs. Furthermore, the oxidation patterns reveal that decolorization of AB-25 results in the formation of sulfates due to desulfonation.

Considerable researches on removal of azo dyes have been reported in recent years, but few researchers have documented adsorption and/or transformation of anthraquinone dyes by physical, chemical, or biological treatment methods due to their fused aromatic structures. In this study, tea residue was found to have significant enhancement effect on the decolorization of anthraquinone dye reactive blue 19. This effect worked on different dye decolorizing bacterial florae and the natural bacterial flora from surface water and exhibited universal feature. Six single bacterial strains were isolated from bacterial flora DDMY2. Unexpectedly, all of them had poor decolorization capacity. High-throughput sequencing results revealed the community evolution of bacterial flora DDMY2 cultured with tea residue after 6 months and 12 months. It was found that the community structure changed dramatically because the influence of tea residue and the dominant functional genera, such as unclassified_o_Pseudomonadales, Stenotrophomonas, Bordetella, and Brevibacillus, was significantly enriched. Meanwhile, the evolved community structure could keep stable for a long time, resulting in the decolorization effect stabilized for a long time. This study provides the tea residue as the bioactivator that can be applied to boost the decolorization of dyes by various potential bacterial florae. It also enlarges our knowledge of making full use of biowaste in biological wastewater treatment.

The textile industry creates environmental problems due to the release of highly polluting effluents containing substances from different stages of dyeing that are resistant to light, water, and various chemicals, and most of them are difficult to decolorize because of its synthetic origin. The biological degradation of dyes is an economical and environmentally friendly alternative. The aim of this work was to use biofilms of basidiomycete fungi isolated from the Peruvian rainforest for the decolorization of synthetic reactive dyes, considering the advantages of these systems which include better contact with the surrounding medium, resistance to chemical and physical stress, and higher metabolic activity. Among several isolates, two were selected for their capacity of rapid decolorization of several dyes and their biofilm-forming ability. These strains were molecularly identified as Trametes polyzona LMB-TM5 and Ceriporia sp. LMB-TM1 and used in biofilm cultivation for the decolorization of six reactive dyes and textile effluents. Azo dyes were moderately decolorized by both strains, but Remazol Brilliant Blue R (anthraquinone) and Synozol Turquoise Blue HF-G (phthalocyanine) were highly decolorized (97 and 80 %, respectively) by T. polyzona LMB-TM5. Degradation products were found by HPLC analysis. Simulated effluents made of a mixture of six dyes were moderately decolorized by both strains, but a real textile effluent was highly (93 %) decolorized by T. polyzona LMB-TM5. In summary, T. polyzona LMB-TM5 was more efficient than Ceriporia sp. LMB-TM1 for the decolorization of textile dyes and effluents at high initial rates enabling the development of in-plant continuous biofilm processes.

In situ chemical oxidation using persulfate is one alternative to remediate polycyclic aromatic hydrocarbon-contaminated soil; however, oxidation can lead to the formation of toxic and persistent by-products, and treatment efficiency can be dependent on environmental conditions. Temperature and soil matrix properties can dictate reaction rates and pathways, promoting oxidant activation or scavenging the free radicals generated. This research investigated the ability of persulfate to degrade anthracene in tropical environmental conditions. Batch tests were conducted for various persulfate systems (naturally and chelated-iron-activated), with an Oxisol contaminated with anthracene. Electron paramagnetic resonance (EPR) was used to identify free radicals formed. Naturally activated persulfate degraded more than 96% of the anthracene and its by-product anthraquinone after 90 days, considered more toxic and persistent, while the chelated-iron-activated persulfate system used was able to remove 70% of the anthracene. EPR measurements showed the coexistence of SO₄·⁻ and ·OH radicals. Sulfate radicals were formed by thermal activation at ambient temperatures (mean of 23.7 °C), and ·OH was formed by propagation reactions and hydrolysis in acidic conditions that lead to peroxide formation. In the naturally activated system, anthracene degradation was observed and SO₄·⁻ radicals were abundant, indicating that this treatment system can be effective in a typical tropical soil environment.

Difficulties encountered in estimating the biodegradation of poorly water-soluble substances are often linked to their limited bioavailability to microorganisms. Many original bioavailability improvement methods (BIMs) have been described, but no global approach was proposed for a standardized comparison of these. The latter would be a valuable tool as part of a wider strategy for evaluating poorly water-soluble substances. The purpose of this study was to define an evaluation strategy following the assessment of different BIMs adapted to poorly water-soluble substances with ready biodegradability tests. The study was performed with two poorly water-soluble chemicals—a solid, anthraquinone, and a liquid, isodecyl neopentanoate—and five BIMs were compared to the direct addition method (reference method), i.e., (i) ultrasonic dispersion, (ii) adsorption onto silica gel, (iii) dispersion using an emulsifier, (iv) dispersion with silicone oil, and (v) dispersion with emulsifier and silicone oil. A two-phase evaluation strategy of solid and liquid chemicals was developed involving the selection of the most relevant BIMs for enhancing the biodegradability of tested substances. A description is given of a BIM classification ratio (R BIM), which enables a comparison to be made between the different test chemical sample preparation methods used in the various tests. Thereby, using this comparison, the BIMs giving rise to the greatest biodegradability were ultrasonic dispersion and dispersion with silicone oil or with silicone oil and emulsifier for the tested solid chemical, adsorption onto silica gel, and ultrasonic dispersion for the liquid one.