Degradation of triclosan by environmental microbial consortia and by axenic cultures of microorganisms with concerns to wastewater treatment

Tailoring CuOx loading on CoFe2O4 nanocubes photocatalyst for superior photocatalytic degradation of triclosan pollutants under VL irradiation and toxicological evaluation

In this study, we report the development of a novel CuOx(3 wt%)/CoFe2O4 nanocubes (NCs) photocatalyst through simple co-precipitation and wet impregnation methods for the efficient photocatalytic degradation of triclosan (TCS) pollutants. Initially, rod-shaped bare CoFe2O4 was synthesized using a simple co-precipitation technique. Subsequently, CuOx was loaded in various percentages (1, 2, and 3 wt%) onto the surface of bare CoFe2O4 nanorods (NRs) via the wet impregnation method. The synthesized materials were systematically characterized to evaluate their composition, structural and electrical characteristics. The CuOx(3 wt%)/CoFe2O4 NCs photocatalyst exhibited superior photocatalytic degradation efficiency of TCS (89.9%) compared to bare CoFe2O4 NRs (62.1 %), CuOx(1 wt%)/CoFe2O4 (80.1 %), CuOx(2 wt%)/CoFe2O4 (87.0 %) under visible light (VL) irradiation (λ ≥ 420 nm), respectively. This enhanced performance was attributed to the improved separation effectiveness of photogenerated electron (e-) and hole (h+) in CuOx(3 wt%)/CoFe2O4 NCs. Furthermore, the optimized CuOx(3 wt%)/CoFe2O4 NCs exhibited strong stability and reusability in TCS degradation, as demonstrated by three successive cycles. Genetic screening on Caenorhabditis elegans showed that CuOx(3 wt%)/CoFe2O4 NCs reduced ROS-induced oxidative stress during TCS photocatalytic degradation. ROS levels decreased at 30, 60, and 120-min intervals during TCS degradation, accompanied by improved egg hatching rates. Additionally, expression levels of stress-responsible antioxidant proteins like SOD-3GFP and HSP-16.2GFP were significantly normalized. This study demonstrates the efficiency of CuOx(3 wt%)/CoFe2O4 NCs in degrading TCS pollutants, offers insights into toxicity dynamics, and recommends its use for future environmental remediation.

Unveiling microbial degradation of triclosan: Degradation mechanism, pathways, and catalyzing clean energy

Emerging organic contaminants present in the environment can be biodegraded in anodic biofilms of microbial fuel cells (MFCs). However, there is a notable gap existing in deducing the degradation mechanism, intermediate products, and the microbial communities involved in degradation of broad-spectrum antibiotic such as triclosan (TCS). Herein, the possible degradation of TCS is explored using TCS acclimatized biofilms in MFCs. 95% of 5 mgL-1 TCS are been biodegraded within 84 h with a chemical oxygen demand (COD) reduction of 62% in an acclimatized-MFC (A-MFC). The degradation of TCS resulted in 8 intermediate products including 2,4 -dichlorophenol which gets further mineralized within the system. Concurrently, the 16S rRNA V3-V4 sequencing revealed that there is a large shift in microbial communities after TCS acclimatization and MFC operation. Moreover, 30 dominant bacterial species (relative intensity >1%) are identified in the biofilm in which Sulfuricurvum kujiense, Halomonas phosphatis, Proteiniphilum acetatigens, and Azoarcus indigens significantly contribute to dihydroxylation, ring cleavage and dechlorination of TCS. Additionally, the MFC was able to produce 818 ± 20 mV voltage output with a maximum power density of 766.44 mWm-2. The antibacterial activity tests revealed that the biotoxicity of TCS drastically reduced in the MFC effluent, signifying the non-toxic nature of the degraded products. Hence, this work provides a proof-of-concept strategy for sustainable mitigation of TCS in wastewaters with enhanced bioelectricity generation.

Uptake, tissue distribution, and biotransformation pattern of triclosan in tilapia exposed to environmentally-relevant concentrations

Although triclosan has been ubiquitously detected in aquatic environment and is known to have various adverse effects to fish, details on its uptake, bioconcentration, and elimination in fish tissues are still limited. This study investigated the uptake and elimination toxicokinetics, bioconcentration, and biotransformation potential of triclosan in Nile tilapia (Oreochromis niloticus) exposed to environmentally-relevant concentrations under semi-static regimes for 7 days. For toxicokinetics, triclosan reached a plateau concentration within 5-days of exposure, and decreased to stable concentration within 5 days of elimination. Approximately 50 % of triclosan was excreted by fish through feces, and up to 29 % of triclosan was excreted through the biliary excretion. For fish exposed to 200 ng·L-1, 2000 ng·L-1, and 20,000 ng·L-1, the bioconcentration factors (log BCFs) of triclosan in fish tissues obeyed similar order: bile ≈ intestine > gonad ≈ stomach > liver > kidney ≈ gill > skin ≈ plasma > brain > muscle. The log BCFs of triclosan in fish tissues are approximately maintained constants, no matter what triclosan concentrations in exposure water. Seven biotransformation products of triclosan, involved in both phase I and phase II metabolism, were identified in this study, which were produced through hydroxylation, bond cleavages, dichlorination, and sulfation pathways. Metabolite of triclosan-O-sulfate was detected in all tissues of tilapia, and more toxic product of 2,4-dichlorophenol was also found in intestine, gonad, and bile of tilapia. Meanwhile, two metabolites of 2,4-dichlorophenol-O-sulfate and monohydroxy-triclosan-O-sulfate were firstly discovered in the skin, liver, gill, intestine, gonad, and bile of tilapia in this study. These findings highlight the importance of considering triclosan biotransformation products in ecological assessment. They also provide a scientific basis for health risk evaluation of triclosan to humans, who are associated with dietary exposure through ingesting fish.

Nanomaterials for Removal of Phenolic Derivatives from Water Systems: Progress and Future Outlooks

Environmental pollution remains one of the most challenging problems facing society worldwide. Much of the problem has been caused by human activities and increased usage of various useful chemical agents that inadvertently find their way into the environment. Triclosan (TCS) and related phenolic compounds and derivatives belong to one class of such chemical agents. In this work, we provide a mini review of these emerging pollutants and an outlook on the state-of-the-art in nanostructured adsorbents and photocatalysts, especially nanostructured materials, that are being developed to address the problems associated with these environmental pollutants worldwide. Of note, the unique properties, structures, and compositions of mesoporous nanomaterials for the removal and decontamination of phenolic compounds and derivatives are discussed. These materials have a great ability to scavenge, adsorb, and even photocatalyze the decomposition of these compounds to mitigate/prevent their possible harmful effects on the environment. By designing and synthesizing them using silica and titania, which are easier to produce, effective adsorbents and photocatalysts that can mitigate the problems caused by TCS and its related phenolic derivatives in the environment could be fabricated. These topics, along with the authors' remarks, are also discussed in this review.

Triclosan and related compounds in the environment: Recent updates on sources, fates, distribution, analytical extraction, analysis, and removal techniques

Triclosan (TCS) has been widely used in daily life because of its broad-spectrum antibacterial activities. The residue of TCS and related compounds in the environment is one of the critical environmental safety problems, and the pandemic of COVID-19 aggravates the accumulation of TCS and related compounds in the environment. Therefore, detecting TCS and related compound residues in the environment is of great significance to human health and environmental safety. The distribution of TCS and related compounds are slightly different worldwide, and the removal methods also have advantages and disadvantages. This paper summarized the research progress on the source, distribution, degradation, analytical extraction, detection, and removal techniques of TCS and related compounds in different environmental samples. The commonly used analytical extraction methods for TCS and related compounds include solid-phase extraction, liquid-liquid extraction, solid-phase microextraction, liquid-phase microextraction, and so on. The determination methods include liquid chromatography coupled with different detectors, gas chromatography and related methods, sensors, electrochemical method, capillary electrophoresis. The removal techniques in various environmental samples mainly include biodegradation, advanced oxidation, and adsorption methods. Besides, both the pros and cons of different techniques have been compared and summarized, and the development and prospect of each technique have been given.

Biotreatment efficiency, degradation mechanism and bacterial community structure in an immobilized cell bioreactor treating triclosan-rich wastewater

Biotreatment of triclosan is mainly performed in conventional activated sludge systems, which, however, are not capable of completely removing this antibacterial agent. As a consequence, triclosan ends up in surface and groundwater, constituting an environmental threat, due to its toxicity to aquatic life. However, little is known regarding the diversity and mechanism of action of microbiota capable of degrading triclosan. In this work, an immobilized cell bioreactor was setup to treat triclosan-rich wastewater. Bioreactor operation resulted in high triclosan removal efficiency, even greater than 99.5%. Nitrogen assimilation was mainly occurred in immobilized biomass, although nitrification was inhibited. Based on Illumina sequencing, Bradyrhizobiaceae, followed by Ferruginibacter, Thermomonas, Lysobacter and Gordonia, were the dominant genera in the bioreactor, representing 38.40 ± 0.62% of the total reads. However, a broad number of taxa (15 genera), mainly members of Xanthomonadaceae, Bradyrhizobiaceae and Chitinophagaceae, showed relative abundances between 1% and 3%. Liquid Chromatography coupled to Quadrupole Time-Of-Flight Mass Spectrometry (LC-QTOF-MS) resulted in the identification of catabolic routes of triclosan in the immobilized cell bioreactor. Seven intermediates of triclosan were detected, with 2,4-dichlorophenol, 4-chlorocatechol and 2-chlorohydroquinone being the key breakdown products of triclosan. Thus, the immobilized cell bioreactor accommodated a diverse bacterial community capable of degrading triclosan.

Evaluating the fate and potential health risks of organochlorine pesticides and triclosan in soil, sediment, and water from Asa Dam River, Ilorin Kwara State, Nigeria

The quest for safe water due to exponential population growth and climate change has stressed the existing available water source. It is crucial to establish the present pollution level of the Asa River and the health risk it may pose to the people. Samples were collected along the Asa River, Ilorin, Kwara State, Nigeria, and treated using standard methods as stipulated by United States Environmental Protection Agency. The treated samples were analyzed and quantified for dieldrin, endrin, dichlorodiphenyltrichloroethane metabolites, mirex, hexachlorocyclohexane, hexachlorobenzene, and triclosan using the gas chromatography-mass spectrometry. The result showed that the levels of organochlorine pesticides (OCPs) ranged from 0.0045-0.947 μg/kg, 0.0036-0.093 μg/kg, and 0.001-0.007 μg/L in sediment, soil, and water samples, respectively. While the mean concentration of triclosan is 3.78 μg/kg, 2.995 μg/kg, and 0.064 μg/L in sediment, soil, and water samples, respectively. The levels of OCPs were lower than the limits in drinking water as set by World Health Organization and European Union. Health risk assessment for both children and adults was evaluated using non-carcinogenic and carcinogenic risk with the hazard quotient (HQ) and was found to be greater than unity (> 1) in children for the targeted OCPs. Associated cancer risk for OCPs ranged from low cancer risk to moderate risk for humans. The adverse ecological effects of OCPs showed to be very rare to occur and frequent effects may not likely occur except for HCH.

Triclosan Promotes Conjugative Transfer of Antibiotic Resistance Genes to Opportunistic Pathogens in Environmental Microbiome

Although triclosan, as a widely used antiseptic chemical, is known to promote the transmission of antibiotic resistance to diverse hosts in pure culture, it is still unclear whether and how triclosan could affect the transmission of broad-host-range plasmids among complex microbial communities. Here, bacterial culturing, fluorescence-based cell sorting, and high-throughput 16S rRNA gene amplicon sequencing were combined to investigate contributions of triclosan on the transfer rate and range of an IncP-type plasmid from a proteobacterial donor to an activated sludge microbiome. Our results demonstrate that triclosan significantly enhances the conjugative transfer of the RP4 plasmid among activated sludge communities at environmentally relevant concentrations. High-throughput 16S rRNA gene sequencing on sorted transconjugants demonstrates that triclosan not only promoted the intergenera transfer but also the intragenera transfer of the RP4 plasmid among activated sludge communities. Moreover, triclosan mediated the transfer of the RP4 plasmid to opportunistic human pathogens, for example, Legionella spp. The mechanism of triclosan-mediated conjugative transfer is primarily associated with excessive oxidative stress, followed by increased membrane permeability and provoked SOS response. Our findings offer insights into the impacts of triclosan on the dissemination of antibiotic resistance in the aquatic environmental microbiome.

Degradation of Triclosan in the Water Environment by Microorganisms: A Review

Triclosan (TCS), a kind of pharmaceuticals and personal care products (PPCPs), is widely used and has had a large production over years. It is an emerging pollutant in the water environment that has attracted global attention due to its toxic effects on organisms and aquatic ecosystems, and its concentrations in the water environment are expected to increase since the COVID-19 pandemic outbreak. Some researchers found that microbial degradation of TCS is an environmentally sustainable technique that results in the mineralization of large amounts of organic pollutants without toxic by-products. In this review, we focus on the fate of TCS in the water environment, the diversity of TCS-degrading microorganisms, biodegradation pathways and molecular mechanisms, in order to provide a reference for the efficient degradation of TCS and other PPCPs by microorganisms.

Transcriptional response of a green alga (Raphidocelis subcapitata) exposed to triclosan: photosynthetic systems and DNA repair

Recent studies show that triclosan (TCS) exposure causes reduction in pigments, suppression of photosynthesis, and induction of oxidative stress at the physiological level, resulting in morphological alteration and growth inhibition in algae including Raphidocelis subcapitata (R. subcapitata, a freshwater model green alga). However, the underlying molecular mechanisms remain to be elucidated, especially at environmentally relevant concentrations. The present study uncovered the transcriptional profiles and molecular mechanisms of TCS toxicity in R. subcapitata using next-generation sequencing. The algal growth was drastically inhibited following a 7-day exposure at both 75 and 100 μg/L TCS, but not at 5 μg/L (environmentally realistic level). The transcriptomic analysis shows that molecular signaling pathways including porphyrin and chlorophyll metabolism, photosynthesis - antenna proteins, and photosynthesis were suppressed in all three TCS treatments, and the perturbations of these signaling pathways were exacerbated with increased TCS exposure concentrations. Additionally, signaling of replication-coupled DNA repair was only activated in 100 μg/L TCS treatment. These results indicate that photosynthesis systems were sensitive targets of TCS toxicity in R. subcapitata, which is distinct from the inhibition of lipid synthesis by TCS in bacteria. This study provides novel knowledge on molecular mechanisms of TCS toxicity in R. subcapitata.

Treatment of triclosan through enhanced microbial biodegradation

Triclosan (TCS) is extensively used in healthcare and personal care products as an antibacterial agent. Due to the persistent and toxic nature of TCS, it is not completely degraded in the biological wastewater treatment process. In this research work, identification of TCS degrading bacteria from municipal wastewater sludge and applying the same as bioaugmentation treatment for wastewater have been reported. Based on the 16S rRNA analysis of wastewater sludge, it was found that Providencia rettgeri MB-IIT strain was active and able to grow in higher TCS concentration. The identified bacterial strain was able to use TCS as carbon and energy source for its growth. The biodegradation experiment was optimized for the operational parameters viz. pH (5-10), inoculum size (1-5% (v/v)) and different initial concentration (2, 5, and 10 mg/L) of TCS. During the TCS degradation process, manganese peroxidase (MnP) and laccase (LAC) enzyme activity and specific growth rate of P. rettgeri strain were maximum at pH=7% and 2% (v/v) inoculum size, resulting in 98% of TCS removal efficiency. A total of six intermediate products were identified from the Liquid chromatography-high-resolution mass spectrometry (LC-HRMS) analysis, and the two mechanisms responsible for the degradation of TCS have been elucidated. The study highlights that P. rettgeri MB-IIT strain could be advantageously used to degrade triclosan present in the wastewater.

Effect of Pleurotus ostreatus and Trametes versicolor on triclosan biodegradation and activity of laccase and manganese peroxidase enzymes

INTRODUCTION

Triclosan (TCS) is an extensively used antibacterial agent which has been frequently detected in different environmental compartments. Because of TCS inhibition effect on vast majority of bacterial species, it is important to explore fungal species and their involved enzymes in TCS biodegradation. The aim of this study was to compare the potential of two white rot fungi Pleurotus ostreatus and Trametes versicolor for TCS biodegradation through the whole cell culture of fungi in an aqueous culture medium. Additionally, the changes in ligninolytic enzyme activities and possible correlations and contributions of degradative enzymes during TCS biodegradation process were monitored.

MATERIAL AND METHODS

This study was carried out using a factorial experiment with a completely randomized design in three replications. factorial design in The experimental factors included: two white rot fungi Pleurotus ostreatus and Trametes versicolor and uninoculated controls which were subjected to five levels of TCS concentrations (0, 5, 10, 20, 30 and 50 μg mL-1) to assess ligninolytic enzymatic activity during biodegradation of TCS. Samples were harvested periodically at three time intervals (4, 7 and 10 days). An AB SCIEX 3200 QTRAP LC-MS/MS system was used in order to analyze the biodegradation of TCS in liquid medium.

RESULTS

Results suggested that the two white rot fungi responded differently when exposed to the different concentrations of TCS. In general, P. ostreatus exhibited more potential and ligninolytic enzymatic activity compared to T. versicolor. LC-MS/MS analyses also showed that P. ostreatus degraded TCS with higher efficiency compared to T. versicolor. In addition, almost all P. ostreatus biodegradation activity was completed within the first day of sampling. Contrasting, less efficient degradation was observed by T. versicolor, reaching around 88% of TCS biodegradation at concentration of 20 μg mL-1after 10 days. At higher TCS concentrations (≥30 μg mL-1), the growth of T. versicolor severely inhibited and led to a drop in enzymatic activity and biodegradation. Furthermore, laccase and manganese peroxidase (MnP) were determined as more involved enzymes which significantly correlated to TCS biodegradation by T. versicolor and P. ostreatus, respectively.

CONCLUSION

P. ostreatus might be considered as efficient fungus in biodegradation of high amount of TCS in environmental matrices. The results of the present study might provide insights for future investigations on potential of fungi for applications in bioaugmentation-based strategies to remove TCS from wastewater and activated sludge.

From Laboratory Tests to the Ecoremedial System: The Importance of Microorganisms in the Recovery of PPCPs-Disturbed Ecosystems

The presence of a wide variety of emerging pollutants in natural water resources is an important global water quality challenge. Pharmaceuticals and personal care products (PPCPs) are known as emerging contaminants, widely used by modern society. This objective ensures availability and sustainable management of water and sanitation for all, according to the 2030 Agenda. Wastewater treatment plants (WWTP) do not always mitigate the presence of these emerging contaminants in effluents discharged into the environment, although the removal efficiency of WWTP varies based on the techniques used. This main subject is framed within a broader environmental paradigm, such as the transition to a circular economy. The research and innovation within the WWTP will play a key role in improving the water resource management and its surrounding industrial and natural ecosystems. Even though bioremediation is a green technology, its integration into the bio-economy strategy, which improves the quality of the environment, is surprisingly rare if we compare to other corrective techniques (physical and chemical). This work carries out a bibliographic review, since the beginning of the 21st century, on the biological remediation of some PPCPs, focusing on organisms (or their by-products) used at the scale of laboratory or scale-up. PPCPs have been selected on the basics of their occurrence in water resources. The data reveal that, despite the advantages that are associated with bioremediation, it is not the first option in the case of the recovery of systems contaminated with PPCPs. The results also show that fungi and bacteria are the most frequently studied microorganisms, with the latter being more easily implanted in complex biotechnological systems (78% of bacterial manuscripts vs. 40% fungi). A total of 52 works has been published while using microalgae and only in 7% of them, these organisms were used on a large scale. Special emphasis is made on the advantages that are provided by biotechnological systems in series, as well as on the need for eco-toxicological control that is associated with any process of recovery of contaminated systems.

Associations of Prenatal Exposure to Triclosan and Maternal Thyroid Hormone Levels: A Systematic Review and Meta-Analysis

OBJECTIVE

To quantitatively evaluate associations between exposure to triclosan during pregnancy and maternal thyroid hormone levels.

METHOD

The databases of PubMed, Embase, Web of Science and Cochrane Library were systematically searched to identify relevant studies on the relationship between prenatal exposure to triclosan and maternal levels of serum thyroid hormone published before October 22, 2019. Stata 12.0 was used to examine the heterogeneity among the eligible studies.

RESULTS

Seven studies involving a total of 4,136 participants were included. Overall, descriptive analysis provided no indication that exposure to TCS during pregnancy was related to either maternal FT4 levels (ES = 0.01, 95% CI: -0.03 to 0.05, P = 0.00) or TSH levels (ES = -0.03, 95% CI: -0.13 to 0.07, P = 0.412). Although the results were statistically insignificant, with the increase of urine TCS concentration, maternal FT4 levels exhibited a tendency to increase while TSH levels had a tendency to decrease during pregnancy.

CONCLUSION

The results indicated that exposure to triclosan during pregnancy has no significant influence on maternal levels of thyroid hormone. On account of the inconsistency of existing research designs and study locations, further studies and replication are necessary to confirm these findings.