Complete 2,4,6-trichlorophenol degradation by anaerobic sludge acclimated with 4-chlorophenol: Synergetic effect of nZVI@BMPC and sodium lactate as an external nutrient.

Ball-milled plastic char supported nano zero-valent iron (nZVI@BMPC) and their application combined with anaerobic sludge for microbial dechlorination of 2,4,6-trichlorophenol (2,4,6-TCP) were investigated. The XRD and FTIR analysis proved composition of zero valent states of iron, and the BET and SEM analysis showed that nZVI was uniformly distributed on the surface of BMPC. Successive addition of 1000 mg/L sodium lactate and nZVI@BMPC enhanced the acclamation of anaerobic sludge and resulted in the degradation of 4-CP within 80 days. The acclimated consortium with nZVI@BMPC completely degraded 2,4,6-TCP into CH4 and CO2, and the key dechlorination route was through 4-CP dechlorinaion and mineralization. The degradation rate of 2,4,6-TCP with nZVI@BMPC was 0.22/d, greater than that without nZVI@BMPC. The dechlorination efficiency was enhanced in the Fe2+/Fe3+ system controlled by nZVI@BMPC and iron-reducing bacteria. Metagenomic analysis result showed that the dominant de-chlorinators were Chloroflexi sp., Desulfovibrio, and Pseudomonas, which could directly degrade 2,4,6-TCP to 4-CP, especially, Chloroflexi bacterium could concurrently be used to mineralize 4-CP. The relative abundance of the functional genes cprA, acoA, acoB, and tfdB increased significantly in the presence of the nZVI@BMPC. This study provides a new strategy can be a good alternative for possible application in groundwater remediation.

Ammonia monooxygenase-mediated cometabolic biotransformation of volatile 4-chlorophenol in nitrifying counter-diffused biofilms: A combined molecular dynamics simulation, DFT calculation and experimental study.

Ammonia monooxygenase (AMO)-mediated cometabolism of organic pollutants has been widely observed in biological nitrogen removal process. However, its molecular mechanism remains unclear, hindering its practical application. Furthermore, conventional nitrification systems encounter significant challenges such as air pollution and the loss of ammonia-oxidizing bacteria, when dealing with wastewater containing volatile organic pollutants. This study developed a nitrifying membrane-aerated biofilm reactor (MABR) to enhance the biodegradation of volatile 4-chlorophenol (4-CP). Results showed that 4-CP was primarily removed via Nitrosomonas nitrosa-mediated cometabolism in the presence of NH4+-N, supported by the increased nicotinamide adenine dinucleotide (NADH) and adenosine triphosphate (ATP) content, AMO activity and the related genes abundance. Hydroquinone, detected for the first time and produced via oxidative dechlorination, as well as 4-chlorocatechol was primary transformation products of 4-CP. Nitrosomonas nitrosa AMO structural model was constructed for the first time using homology modeling. Molecular dynamics simulation suggested that the ortho-carbon in the benzene ring of 4-CP was more prone to metabolismcompared to the ipso-carbon. Density functional theory calculation revealed that 4-CP was metabolized by AMO via H-abstraction-OH-rebound reaction, with a significantly higher rebound barrier at the ipso-carbon (16.37 kcal·mol-1) as compared to the ortho-carbon (6.7 kcal·mol-1). This study fills the knowledge gap on the molecular mechanism of AMO-mediated cometabolism of organic pollutants, providing practical and theoretical foundations for improving volatile organic pollutants removal through nitrifying MABR.

Cu-chelated polydopamine nanozymes with laccase-like activity for photothermal catalytic degradation of dyes.

The industrial applications of enzymes are usually hindered by the high production cost, intricate reusability, and low stability in terms of thermal, pH, salt, and storage. Therefore, the de novo design of nanozymes that possess the enzyme mimicking biocatalytic functions sheds new light on this field. Here, we propose a facile one-pot synthesis approach to construct Cu-chelated polydopamine nanozymes (PDA-Cu NPs) that can not only catalyze the chromogenic reaction of 2,4-dichlorophenol (2,4-DP) and 4-aminoantipyrine (4-AP), but also present enhanced photothermal catalytic degradation for typical textile dyes. Compared with natural laccase, the designed mimic has higher affinity to the substrate of 2,4-DP with Km of 0.13 mM. Interestingly, PDA-Cu nanoparticles are stable under extreme conditions (temperature, ionic strength, storage), are reusable for 6 cycles with 97 % activity, and exhibit superior substrate universality. Furthermore, PDA-Cu nanozymes show a remarkable acceleration of the catalytic degradation of dyes, malachite green (MG) and methylene blue (MB), under near-infrared (NIR) laser irradiation. These findings offer a promising paradigm on developing novel nanozymes for biomedicine, catalysis, and environmental engineering.

Construction of biochar-based organohalide-respiring bacterial agent for remediation of 2,4,6-trichlorophenol contaminated soil.

Construction of an efficient bio-reductive dechlorination system remains challenging due to the narrow ecological niche and low-growth rate of organohalide-respiring bacteria during field remediation. In this study, a biochar-based organohalide-respiring bacterial agent was obtained, and its performance and effects on indigenous microbial composition, diversity, and inter-relationship in soil were investigated. A well-performing material, Triton X-100 modified biochar (BC600-TX100), was found to have the superior average pore size, specific surface area and hydrophicity, compared to other materials. Interestingly, Pseudomonas aeruginosa CP-1, which is capable of 2,4,6-TCP dechlorination, showed a 348 times higher colonization cell number on BC600-TX100 than that of BC600 after 7 d. Meanwhile, the dechlorination rate in soil showed the highest (0.732 d-1) in the BC600-TX100 bacterial agent than in the other agents. The long-term performance of the BC600-TX100 OHRB agent was also verified, with a stable dechlorination activity over six cycles. Soil microbial community analysis found the addition of the BC600-TX100 OHRB agent significantly increased the relative abundance of genus Pseudomonas from 1.53 % to 11.2 %, and Pseudomonas formed a close interaction relationship with indigenous microorganisms, creating a micro-ecological environment conducive to reductive dechlorination. This study provides a feasible bacterial agent for the in-situ bioremediation of soil contaminated organohalides. ENVIRONMENTAL IMPLICATION: Halogenated organic compounds are a type of toxic, refractory, and bio-accumulative persistent compounds widely existed in environment, widely detected in the air, water, and soil. In this study, we provide a feasible bacterial agent for the in-situ bioremediation of soil contaminated halogenated organic compounds. The application of biochar provides new insights for "Turning waste into treasure", which meets with the concept of green chemistry.

Identification of UDP-glucuronosyltransferase (UGT) isoforms involved in the metabolism of Chlorophenols (CPs).

Chlorophenols (CPs) are a group of pollutants that pose a great threat to the environment, they are widely used in industrial and agricultural wastes, pesticides, herbicides, textiles, pharmaceuticals and plastics. Among CPs, pentachlorophenol was listed as one of the persistent organic pollutants (POPs) by the Stockholm convention. This study aims to identify the UDP-glucosyltransferase (UGT) isoforms involved in the metabolic elimination of CPs. CPs' mono-glucuronide was detected in the human liver microsomes (HLMs) incubation mixture with co-factor uridine-diphosphate glucuronic acid (UDPGA). HLMs-catalyzed glucuronidation metabolism reaction equations followed Michaelis-Menten or substrate inhibition type. Recombinant enzymes and chemical reagents inhibition experiments were utilized to phenotype the main UGT isoforms involved in the glucuronidation of CPs. UGT1A6 might be the major enzyme in the glucuronidation of mono-chlorophenol isomer. UGT1A1, UGT1A6, UGT1A9, UGT2B4 and UGT2B7 were the most important five UGT isoforms for metabolizing the di-chlorophenol and tri-chlorophenol isomers. UGT1A1 and UGT1A3 were the most important UGT isoforms in the catalysis of tetra-chlorophenol and pentachlorophenol isomers. Species differences were investigated using rat liver microsomes (RLMs), pig liver microsomes (PLMs), dog liver microsomes (DLMs), and monkey liver microsomes (MyLMs). All these results were helpful for elucidating the metabolic elimination and toxicity of CPs.

How halogenated aromatic compounds affect the electron supply and consumption in glucose supported denitrification?

Halogenated aromatic compounds possess bidirectional effects on denitrifying bio-electron behavior, providing electrons and potentially interfering with electron consumption. This study selected the typical 4-chlorophenol (4-CP, 0-100 mg/L) to explore its impact mechanism on glucose-supported denitrification. When COD(glucose)/COD(4-CP)=28.70-3.59, glucose metabolism remained the dominant electron supply process, although its removal efficiency decreased to 73.84-49.66 %. When COD(glucose)/COD(4-CP)=2.39-1.43, 4-CP changed microbial carbon metabolism priority by inhibiting the abundance of glucose metabolizing enzymes, gradually replacing glucose as the dominant electron donor. Moreover, 5-100 mg/L 4-CP reduced adenosine triphosphate (ATP) by 15.52-24.67 % and increased reactive oxygen species (ROS) by 31.13-63.47 %, causing severe lipid peroxidation, thus inhibiting the utilization efficiency of glucose. Activated by glucose, 4-CP dechlorination had stronger electron consumption ability than NO2--N reduction (NO3--N > 4-CP > NO2--N), combined with the decreased nirS and nirK genes abundance, resulting in NO2--N accumulation. Compared with the blank group (0 mg/L 4-CP), 5-40 mg/L and 60-100 mg/L 4-CP reduced the secretion of cytochrome c and flavin adenine dinucleotides (FAD), respectively, further decreasing the electron transfer activity of denitrification system. Micropruina, a genus that participated in denitrification based on glucose, was gradually replaced by Candidatus_Microthrix, a genus that possessed 4-CP degradation and denitrification functions after introducing 60-100 mg/L 4-CP.

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.

Bioremediation of 2,4,6-trichlorophenol by extracellular enzymes of white rot fungi immobilized with sodium alginate/hydroxyapatite/chitosan microspheres.

Hydroxyapatite, a calcium phosphate biomass material known for its excellent biocompatibility, holds promising applications in water, soil, and air treatment. Sodium alginate/hydroxyapatite/chitosan (SA-HA-CS) microspheres were synthesized by cross-linking sodium alginate with calcium chloride. These microspheres were carriers for immobilizing extracellular crude enzymes from white rot fungi through adsorption, facilitating the degradation of 2,4,6-trichlorophenol (2,4,6-TCP) in water and soil. At 50 °C, the immobilized enzyme retained 87.2% of its maximum activity, while the free enzyme activity dropped to 68.86%. Furthermore, the immobilized enzyme maintained 68.09% of its maximum activity at pH 7, surpassing the 51.16% observed for the free enzyme. Under optimal conditions (pH 5, 24 h), the immobilized enzymes demonstrated a remarkable 94.7% removal rate for 160 mg/L 2,4,6-TCP, outperforming the 62.1% achieved by free crude enzymes. The degradation of 2,4,6-TCP by immobilized and free enzymes adhered to quasi-first-order degradation kinetics. Based on LC-MS, the plausible biodegradation mechanism and reaction pathway of 2,4,6-TCP were proposed, with the primary degradation product identified as 1,2,4-trihydroxybenzene. The immobilized enzyme effectively removed 72.9% of 2,4,6-TCP from the soil within 24 h. The degradation efficiency of the immobilized enzyme varied among different soil types, exhibiting a negative correlation with soil organic matter content. These findings offer valuable insights for advancing the application of immobilized extracellular crude enzymes in 2,4,6-TCP remediation.

Batch-mode degradation of high-strength phenolic pollutants by Pseudomonas aeruginosa strain STV1713 immobilized on single and hybrid matrices.

Controlled environments are pivotal in all bioconversion processes, influencing the efficacy of biocatalysts. In this study, we designed a batch bioreactor system with a packed immobilization column and a decontamination chamber to enhance phenol and 2,4-dichlorophenol degradation using the hyper-tolerant bacterium Pseudomonas aeruginosa STV1713. When free cells were employed to degrade phenol and 2,4-DCP at a concentration of 1000 mg/L, the cells completely removed the pollutants within 28 h and 66 h, respectively. Simultaneous reductions in chemical oxygen demand and biological oxygen demand were observed (phenol: 30.21 mg/L/h and 16.92 mg/L/h, respectively; 2,4-dichlorophenol: 12.85 mg/L/h and 7.21 mg/L/h, respectively). After assessing the degradation capabilities, the bacterium was immobilized on various matrices (sodium alginate, alginate-chitosan-alginate and polyvinyl alcohol-alginate) to enhance pollutant removal. Hybrid immobilized cells exhibited greater tolerance and degradation capabilities than those immobilized in a single matrix. Among them, polyvinyl alcohol-alginate immobilized cells displayed the highest degradation capacities (up to 2000 mg/L for phenol and 2500 mg/L for 2,4-dichlorophenol). Morphological analysis of the immobilized cells revealed enhanced cell preservation in hybrid matrices. Furthermore, the elucidation of the metabolic pathway through the catechol dioxygenase enzyme assay indicated higher activity of the catechol 1,2-dioxygenase enzyme, suggesting that the bacterium employed an ortho-degradation mechanism for pollutant removal. Additionally, enzyme zymography confirmed the presence of catechol 1,2-dioxygenase, with the molecular weight of the enzyme determined as 245 kDa.

Glymphatic fluid transport is suppressed by the aquaporin-4 inhibitor AER-271.

The glymphatic system transports cerebrospinal fluid (CSF) into the brain via arterial perivascular spaces and removes interstitial fluid from the brain along perivenous spaces and white matter tracts. This directional fluid flow supports the clearance of metabolic wastes produced by the brain. Glymphatic fluid transport is facilitated by aquaporin-4 (AQP4) water channels, which are enriched in the astrocytic vascular endfeet comprising the outer boundary of the perivascular space. Yet, prior studies of AQP4 function have relied on genetic models, or correlated altered AQP4 expression with glymphatic flow in disease states. Herein, we sought to pharmacologically manipulate AQP4 function with the inhibitor AER-271 to assess the contribution of AQP4 to glymphatic fluid transport in mouse brain. Administration of AER-271 inhibited glymphatic influx as measured by CSF tracer infused into the cisterna magna and inhibited increases in the interstitial fluid volume as measured by diffusion-weighted MRI. Furthermore, AER-271 inhibited glymphatic efflux as assessed by an in vivo clearance assay. Importantly, AER-271 did not affect AQP4 localization to the astrocytic endfeet, nor have any effect in AQP4 deficient mice. Since acute pharmacological inhibition of AQP4 directly decreased glymphatic flow in wild-type but not in AQP4 deficient mice, we foresee AER-271 as a new tool for manipulation of the glymphatic system in rodent brain.

Búsqueda intencionada y reclasificación de muertes maternas en México: el efecto en la distribución de las causas / Intentional search and reclassification of maternal deaths in Mexico: The effect on the distribution of causes

Objetivo. Corregir la mala clasificación y mejorar la calidad de la información sobre la mortalidad materna en México. Material y métodos. A través de los registros clínicos y autopsias verbales, se estudiaron todas las defunciones certificadas como maternas y una selección de defunciones de mujeres en edad fértil, cuyas causas fueron consideradas como sospechosas de encubrir una muerte materna; todas ocurridas durante 2011 en México. Resultados. La búsqueda intencionada y reclasificación de muertes maternas permitió rescatar más de 100 muertes que no habían sido registradas ni codificadas inicialmente como maternas y se ratificaron o rectificaron las causas anotadas en los certificados de defunción. Este procedimiento también permitió reclasificar como muertes maternas 297 defunciones de la base preliminar del Instituto Nacional de Estadística y Geografía. Conclusiones. La Búsqueda Intencionada y Reclasificación de Muertes Maternas es un procedimiento muy útil para mejorar la calidad de la información sobre la mortalidad materna.

Objective. To correct the misclassification and improve the quality of information on maternal mortality in Mexico. Materials and methods. Using clinical records and verbal autopsies, we studied all deaths certified as maternal deaths as well as a selection of deaths of women of childbearing age whose causes were considered as suspected of hiding a maternal death, all of which occurred during 2011 within Mexico. Results. The deliberate search of maternal deaths and reclassification allowed the rescue of just over 100 deaths that were not originally registered or coded as maternal and confirmed or corrected the causes of death recorded on death certificates as confirmed maternal deaths. This procedure also allowed the reclassification of 297 maternal deaths of women in the groundwork of the National Institute of Statistics and Geography. Conclusions. International Search and Reclassification of Maternal Deaths is a very useful procedure for improving the classification of cases that were not classified as maternal deaths and the effect was greater with the coding of indirect obstetric deaths.

Enhancement with inducers of lacasse production by some strains and application of enzyme to dechlorination of 2, 4, 5-trichlorophenol

Lacasse is one of the extracellular enzymes excreted from white and brown rot fungi, which is involved in ligninolysis. In the present study, the effects of the addition of lacasse inducers to the medium on enhancement of enzyme production under conditions of submerged fermentation were researched. At first, a culture medium was selected suitable for lacasse production. To increase the production of lacasse using different inducers and to examine the ability of dechlorination, this article focuses on screen lacasse activity of 21 basidiomycetes isolates grown in five culture media. All inducers evaluated influenced lacasse activity positively except for gallic acid, mannitol, and malt extract for studied isolates. Our findings showed that lacasse activity of Trametes versicolor ATCC (200801) when it was induced with wheat bran reached up to 29.08 U ml-1 and was examined the ability of dechlorination of 2, 4, 5-trichlorophenol (2,4,5-TCP). The parameters including pH, initial substrate concentration, amount of enzyme, period of reaction, and temperature were tested for dechlorination process. Correlation between oxygen consumption and dechlorination processes under the determined optimum conditions was analyzed. Toxicity of 2, 4, 5-TCP before and after enzymatic treatment was evaluated by Microtox test. The results demonstrated that toxicity of intermediates formed 2, 4, 5-TCP did not change.