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This paper presented the preparation, characterization, and adsorption properties of Brazil nut shell activated carbon for catechol removal from aqueous solutions. The equilibrium adsorption of catechol molecules on this activated was experimentally quantified at pH 6 and temperatures ranging from 25 to 55 °C, and at 25 °C and pH ranging from 6 to 10. These results were utilized to elucidate the role of surface functionalities through statistical physics calculations. All these experimental adsorption isotherms were fitted and interpreted via a monolayer model with one energy, which was chosen as the optimal model. Model physicochemical parameters, which may be categorized as stereographic parameters such as the maximum adsorbed quantity ( Q M ), the number of adsorbed catechol molecules per one Brazil nut shell activated carbon binding site ( n ), and the number of effectively occupied binding sites ( N M ) and energetic parameter such as the half saturation concentration ( C HS ), were analyzed. Microscopically speaking, these modeling results were employed to stereographically and energetically investigate the phenol derivative adsorption mechanism. The maximum catechol adsorbed quantities on this activated carbon ranged from 89.98 to 103.16 mg/g under the tested operating conditions. The adsorption of catechol molecules was found to be exothermic where the maximum adsorbed quantity augmented with solution temperature and the maximum adsorption efficiency was found 103.16 mg/g at 55 °C. In addition, it was found that the catechol molecules were adsorbed with nonparallel orientations on the activated carbon adsorbent since the numbers of catechol molecules per site were superior to 1 (1.10 <  n  < 1.86). Moreover, the calculated molar adsorption energies, which varied between 19.04 and 22.37 kJ/mol, showed exothermic ( ΔE  > 0) and physical ( ΔE  < 40 kJ/mol) adsorption process involving hydrogen bonds, π-π interactions, electron donor-acceptor interactions, and dispersion forces. Finally, the tested adsorbent exhibited unimodal pore size and site energy distributions with peaks centered at pore radius ranging from 2.26 to 2.68 nm, and at adsorption energy ranging from 20.01 to 23.78 kJ/mol, respectively. Macroscopically speaking, three thermodynamic potentials, including the adsorption entropy, internal energy of adsorption, and Gibbs free energy, suggested that the adsorption of catechol on Brazil nut shell activated carbon was a spontaneous and exothermic mechanism.

This article summarizes the current knowledge about the presence of naproxen in the environment, its toxicity to nontarget organisms and the microbial degradation of this drug.Currently, naproxen has been detected in all types of water, including drinking water and groundwater. The concentrations that have been observed ranged from ng/L to μg/L. These concentrations, although low, may have a negative effect of long-term exposure on nontarget organisms, especially when naproxen is mixed with other drugs. The biological decomposition of naproxen is performed by fungi, algae and bacteria, but the only well-described pathway for its complete degradation is the degradation of naproxen by Bacillus thuringiensis B1(2015b). The key intermediates that appear during the degradation of naproxen by this strain are O-desmethylnaproxen and salicylate. This latter is then cleaved by 1,2-salicylate dioxygenase or is hydroxylated to gentisate or catechol. These intermediates can be cleaved by the appropriate dioxygenases, and the resulting products are incorporated into the central metabolism.Key points•High consumption of naproxen is reflected in its presence in the environment.•Prolonged exposure of nontargeted organisms to naproxen can cause adverse effects.•Naproxen biodegradation occurs mainly through desmethylnaproxen as a key intermediate.

In recent years, the increased intake of ibuprofen has resulted in the presence of the drug in the environment. This work presents results of a study on degradation of ibuprofen at 25 mg L −1 in the presence of glucose, as an additional carbon source by Bacillus thuringiensis B1(2015b). In the cometabolic system, the maximum specific growth rate of the bacterial strain was 0.07 ± 0.01 mg mL −1  h −1 and K sμ 0.27 ± 0.15 mg L −1 . The maximum specific ibuprofen removal rate and the value of the half-saturation constant were q max  = 0.24 ± 0.02 mg mL −1  h −1 and K s  = 2.12 ± 0.56 mg L −1 , respectively. It has been suggested that monooxygenase and catechol 1,2-dioxygenase are involved in ibuprofen degradation by B. thuringiensis B1(2015b). Toxicity studies showed that B. thuringiensis B1(2015b) is more resistant to ibuprofen than other tested organisms. The EC50 of ibuprofen on the B1 strain is 809.3 mg L −1 , and it is 1.5 times higher than the value of the microbial toxic concentration (MTC avg ). The obtained results indicate that B. thuringiensis B1(2015b) could be a useful tool in biodegradation/bioremediation processes.

Extended soil contamination by polychlorinated biphenyls (PCBs) represents a global environmental issue that can hardly be addressed with the conventional remediation treatments. Rhizoremediation is a sustainable alternative, exploiting plants to stimulate in situ the degradative bacterial communities naturally occurring in historically polluted areas. This approach can be enhanced by the use of bacterial strains that combine PCB degradation potential with the ability to promote plant and root development. With this aim, we established a collection of aerobic bacteria isolated from the soil of the highly PCB-polluted site \"SIN Brescia-Caffaro\" (Italy) biostimulated by the plant Phalaris arundinacea. The strains, selected on biphenyl and plant secondary metabolites provided as unique carbon source, were largely dominated by Actinobacteria and a significant number showed traits of interest for remediation, harbouring genes homologous to bphA, involved in the PCB oxidation pathway, and displaying 2,3-catechol dioxygenase activity and emulsification properties. Several strains also showed the potential to alleviate plant stress through 1-aminocyclopropane-1-carboxylate deaminase activity. In particular, we identified three Rhodococcus strains able to degrade in vitro several PCB congeners and to promote lateral root emergence in the model plant Arabidopsis thaliana in vivo. In addition, these strains showed the capacity to colonize the root system and to increase the plant biomass in PCB contaminated soil, making them ideal candidates to sustain microbial-assisted PCB rhizoremediation through a bioaugmentation approach.

Contamination of soil and natural water bodies driven by increased organic pollutants remains a universal concern. Naturally, organic pollutants contain carcinogenic and toxic properties threatening all known life forms. The conventional physical and chemical methods employed to remove these organic pollutants ironically produce toxic and non-ecofriendly end-products. Whereas microbial-based degradation of organic pollutants provides an edge, they are usually cost-effective and take an eco-friendly approach towards remediation. Bacterial species, including Pseudomonas , Comamonas , Burkholderia , and Xanthomonas , have the unique genetic makeup to metabolically degrade toxic pollutants, conferring their survival in toxic environments. Several catabolic genes, such as alkB , xylE , catA , and nahAc , that encode enzymes and allow bacteria to degrade organic pollutants have been identified, characterized, and even engineered for better efficacy. Aerobic and anaerobic processes are followed by bacteria to metabolize aliphatic saturated and unsaturated hydrocarbons such as alkanes, cycloalkanes, aldehydes, and ethers. Bacteria use a variety of degrading pathways, including catechol, protocatechuate, gentisate, benzoate, and biphenyl, to remove aromatic organic contaminants such as polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and pesticides from the environment. A better understanding of the principle, mechanisms, and genetics would be beneficial for improving the metabolic efficacy of bacteria to such ends. With a focus on comprehending the mechanisms involved in various catabolic pathways and the genetics of the biotransformation of these xenobiotic compounds, the present review offers insight into the various sources and types of known organic pollutants and their toxic effects on health and the environment.

Since the last few years, the growing interest in the use of natural and synthetic antioxidants as functional food ingredients and dietary supplements, is observed. The imbalance between the number of antioxidants and free radicals is the cause of oxidative damages of proteins, lipids, and DNA. The aim of the study was the review of recent developments in antioxidants. One of the crucial issues in food technology, medicine, and biotechnology is the excess free radicals reduction to obtain healthy food. The major problem is receiving more effective antioxidants. The study aimed to analyze the properties of efficient antioxidants and a better understanding of the molecular mechanism of antioxidant processes. Our researches and sparing literature data prove that the ligand antioxidant properties complexed by selected metals may significantly affect the free radical neutralization. According to our preliminary observation, this efficiency is improved mainly by the metals of high ion potential, e.g., Fe(III), Cr(III), Ln(III), Y(III). The complexes of delocalized electronic charge are better antioxidants. Experimental literature results of antioxidant assays, such as diphenylpicrylhydrazyl (DPPH) and ferric reducing activity power assay (FRAP), were compared to thermodynamic parameters obtained with computational methods. The mechanisms of free radicals creation were described based on the experimental literature data. Changes in HOMO energy distribution in phenolic acids with an increasing number of hydroxyl groups were observed. The antioxidant properties of flavonoids are strongly dependent on the hydroxyl group position and the catechol moiety. The number of methoxy groups in the phenolic acid molecules influences antioxidant activity. The use of synchrotron techniques in the antioxidants electronic structure analysis was proposed.

Catechol dehydroxylation is a central chemical transformation in the gut microbial metabolism of plant- and host-derived small molecules. However, the molecular basis for this transformation and its distribution among gut microorganisms are poorly understood. Here, we characterize a molybdenum-dependent enzyme from the human gut bacterium Eggerthella lenta that dehydroxylates catecholamine neurotransmitters. Our findings suggest that this activity enables E. lenta to use dopamine as an electron acceptor. We also identify candidate dehydroxylases that metabolize additional host- and plant-derived catechols. These dehydroxylases belong to a distinct group of largely uncharacterized molybdenum-dependent enzymes that likely mediate primary and secondary metabolism in multiple environments. Finally, we observe catechol dehydroxylation in the gut microbiotas of diverse mammals, confirming the presence of this chemistry in habitats beyond the human gut. These results suggest that the chemical strategies that mediate metabolism and interactions in the human gut are relevant to a broad range of species and habitats. Inside the human gut there are trillions of bacteria. These microbes are critical for breaking down and modifying molecules that the body consumes (such as nutrients and drugs) and produces (such as hormones). Although metabolizing these molecules is known to impact health and disease, little is known about the specific components, such as the genes and enzymes, involved in these reactions. A prominent microbial reaction in the gut metabolizes molecules by removing a hydroxyl group from an aromatic ring and replacing it with a hydrogen atom. This chemical reaction influences the fate of dietary compounds, clinically used drugs and chemicals which transmit signals between nerves (neurotransmitters). But even though this reaction was discovered over 50 years ago, it remained unknown which microbial enzymes are directly responsible for this metabolism. In 2019, researchers discovered the human gut bacteria Eggerthella lenta produces an enzyme named Dadh that can remove a hydroxyl group from the neurotransmitter dopamine. Now, Maini Rekdal et al. – including many of the researchers involved in the 2019 study – have used a range of different experiments to further characterize this enzyme and see if it can break down molecules other than dopamine. This revealed that Dadh specifically degrades dopamine, and this process promotes E. lenta growth. Next, Maini Rekdal et al. uncovered a group of enzymes that had similar characteristics to Dadh and could metabolize molecules other than dopamine, including molecules derived from plants and nutrients in food. These Dadh-like enzymes were found not only in the guts of humans, but in other organisms and environments, including the soil, ocean and plants. Plant-derived molecules are associated with human health, and the discovery of the enzymes that break down these products could provide new insights into the health effects of plant-based foods. In addition, the finding that gut bacteria harbor a dopamine metabolizing enzyme has implications for the interaction between the gut microbiome and the nervous system, which has been linked to human health and disease. These newly discovered enzymes are also involved in metabolic reactions outside the human body. Future work investigating the mechanisms and outputs of these reactions could improve current strategies for degrading pollutants and producing medically useful molecules.

Melia azedarach- rhizosphere mediated degradation of benzo(a)pyrene (BaP), in the presence of cadmium (Cd) was studied, using efficient rhizobacterial isolate. Serratia marcescens S2I7, isolated from the petroleum-contaminated site, was able to tolerate up to 3.25 mM Cd. In the presence of Cd, the isolate S2I7 exhibited an increase in the activity of stress-responsive enzyme, glutathione-S-transferase. Gas Chromatography-Mass spectroscopy analysis revealed up to 59% in -vitro degradation of BaP after 21 days, while in the presence of Cd, the degradation was decreased by 14%. The bacterial isolate showed excellent plant growth-promoting attributes and could enhance the growth of host plant in Cd contaminated soil. The 52,41,555 bp genome of isolate S. marcescens S2I7 was sequenced, assembled and annotated into 4694 genes. Among these, 89 genes were identified for the metabolism of aromatic compounds and 172 genes for metal resistance, including the efflux pump system. A 2 MB segment of the genome was identified to contain operons for protocatechuate degradation, catechol degradation, benzoate degradation, and an IclR type regulatory protein pcaR , reported to be involved in the regulation of protocatechuate degradation. A pot trial was performed to validate the ability of S2I7 for rhizodegradation of BaP when applied through Melia azedarach rhizosphere. The rhizodegradation of BaP was significantly higher when augmented with S2I7 (85%) than degradation in bulk soil (68%), but decreased in the presence of Cd (71%).

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.

A glassy carbon electrode (GCE) was modified with multi-walled carbon nanotubes (MWCNT) and silver nanoparticles (AgNPs) and applied to the simultaneous determination of hydroquinone (HQ), catechol (CC), bisphenol A (BPA) and phenol by using square-wave voltammetry. The MWCNTs were deposited on the GCE and the AgNPs were then electrodeposited onto the MWCNT/GCE by the application of 10 potential sweep cycles using an AgNP colloidal suspension. The modified GCE was characterized by using SEM, which confirmed the presence of the AgNPs. The electrochemical behavior of the material was evaluated by using cyclic voltammetry, and by electrochemical impedance spectroscopy that employed hexacyanoferrate as an electrochemical probe. The results were compared to the performance of the unmodified GCE. The modified electrode has a lower charge-transfer resistance and yields an increased signal. The peaks for HQ (0.30 V), CC (0.40 V), BPA (0.74 V) and phenol (0.83 V; all versus Ag/AgCl) are well separated under optimized conditions, which facilitates their simultaneous determination. The oxidation current increases linearly with the concentrations of HQ, CC, BPA and phenol. Detection limits are in the order of 1 μM for all 4 species, and the sensor is highly stable and reproducible. The electrode was successfully employed with the simultaneous determination of HQ, CC, BPA and phenol in spiked tap water samples. Graphical abstract A glassy carbon electrode was modified with carbon nanotubes and silver nanoparticles and then successfully applied to the simultaneous determination of four phenolic compounds. The sensor showed high sensitivity in the detection of hydroquinone, catechol, bisphenol A and phenol in water samples.