Tetrahydrofuran (THF)-grown efficient 1,4-dioxane (dioxane)-degrading bacterium,
Arthrobacter
sp. WN18, was used to evaluate its potential for dioxane removal in pure culture and microcosms. Under ...the optimized ratio of THF to dioxane (3:1), WN18 could remove 500 mg/L dioxane by 52.8% ± 0.05% within 8 days and exhibited extraordinary tolerance to THF at concentrations up to 7.0 g/L, indicating that WN18 has a higher tolerance potential for dioxane-degrading activity. Microcosm assays showed that THF alone can effectively stimulate the indigenous microorganisms to remove dioxane, especially when coupled with nutrients. Bioaugmentation results indicated that WN18 can efficiently degrade dioxane, with its concentration decreased from the initial 910 to < 2.0 μg/L within 20 weeks of incubation. The qPCR analyses showed that the abundance of
thmA
gene regulated by different bioremediation strategies correlated with the dioxane biodegradation efficiency in microcosms. Several compounds that are concurrent dioxane contamination could also be utilized by WN18, including benzene and its multiple homologues (e.g., toluene, aniline, and nitrobenzene), while γ-butyrolactone and succinic acid also supported its growth. All these findings indicate that WN18 has great potential for future field applications.
1,4-Dioxane (dioxane), an emerging groundwater contaminant, is frequently detected in landfill leachates with its structural analog, tetrahydrofuran (THF). Along with undesirable leakage of landfill ...leachates, dioxane and THF inevitably percolate into groundwater leading to a broader region of contamination. Cometabolic bioremediation is an effective approach to manage commingled THF and dioxane pollution. In this study, a newly isolated bacterium Arthrobacter sp. WN18 is able to co-oxidize dioxane with THF as the primary substrate. Meanwhile, the THF-induced thmADBC gene cluster was responsible for the dioxane degradation rate indicating THF monooxygenase is the essential enzyme that initializing α-hydroxylation of THF and dioxane. Further, γ-butyrolactone and HEAA were characterized as the key metabolites of THF and dioxane, respectively. In addition, WN18 can tolerate the inhibition of trichloroethylene (5.0 mg/L) as a representative of co-existing leachate constituent, and sustain its activity at various pH (5−11), temperatures (15–42 °C), and salinities (up to 4%, as NaCl wt). Like other Arthrobacter species, WN18 also exhibited the capability of fixing nitrogen. All this evidence indicates the feasibility and advantage of WN18 as a thmADBC-catalyzed inoculator to bioremediate co-contamination of THF and dioxane.
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•The Arthrobacter sp. WN18 was first proved can co-degrade dioxane.•THF-induced thm gene organization that initially cleaved dioxane was identified.•The possible degradation pathway of dioxane and THF were proposed.•WN18 has been shown to degrade dioxane and THF under multiple adverse conditions.
The elimination of 1,4-dioxane (dioxane), a persistent organic pollutant, is a great challenge owing to its high hydrophilicity and chemical stability. Cometabolic bioremediation technology is an ...effective approach to remove many organic pollutants. Because of its eco-friendly and inexpensive properties, molasses is widely used as an auxiliary biomaterial to clean up compound-contaminated sites. In this study, a newly isolated bacterium
Acinetobacter
sp. M21 could effectively remove dioxane using molasses without any apparent lag phase. Under the optimized molasses dosage of 0.3%, M21 could remove 500 mg/L dioxane by 60.0 ± 2.8% within 20 days with a maximum dioxane degradation rate of 1.3 ± 0.2 mg-dioxane/L/h in the first day, and exhibited extraordinary dioxane tolerance up to 1,000 mg/L, while so high dose of dioxane negatively affected the cell growth. The degradation pathway of dioxane was also determined, and was supported by the detection of 2-hydroxyethoxyacetic acid as the key metabolite of dioxane. High level degradation activity of M21 to 20 mg/L dioxane was maintained over a variable of pH (5–11), temperatures (15–45°C), and salinities (up to 8%, as NaCl wt). This is the first report linking the cometabolism of dioxane and molasses by
Acinetobacter
sp. M21, a bacterium that shows great potential for field dioxane bioremediation.
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•A novel Co(II)-FCQDs/FNS catalyst was constructed by lattice VOs adjustment.•The catalyst performed dramatic catalytic activity for MNZ degradation.•The generation of octahedral ...Co(II) boosted the PMS activation performance.•The intrinsic catalytic mechanism in Co(II)-FCQDs/FNS was proposed.
Peroxymonosulfate (PMS) activation by bimetallic Co/Fe oxides, especially spinel FeCo2O4, is a promising way in decontaminating organic pollutants in wastewaters. However, it suffers from low efficiency and the intrinsic catalytic mechanisms are still poorly understood. Therefore, we applied lattice VOs (oxygen vacancies) adjustment strategy to construct a octahedral Co(II)–enriched FeCo2O4 quantum dots anchored on β-FeOOH nanosheets composite (Co(II)-FCQDs/FNS) for boosting PMS activation during the degradation of Metronidazole (MNZ), and pure FeCo2O4 quantum dots (FCQDs) was studied as a comparison. As a result, in PMS/Co(II)-FCQDs/FNS system, 5–30 mg·L−1 MNZ could be completely degraded within 5 min with the usage of 0.05 g·L−1 catalyst, and the degradation efficiency of 100 mg·L−1 MNZ reached 99.92% within 40 min with the PMS utilization of 62.90% at the same condition, whose degradation rate constant was 6.45 times than that of the FCQDs/PMS system. The electron paramagnetic resonance (EPR) and quenching experiments indicated that PMS /Co(II)-FCQDs/FNS system was a pure radical-based (sulfate radicals (SO4•−), hydroxyl radicals (•OH) and superoxide radical (O2•−) oxidation process. Density functional theory (DFT) calculation revealed that the generation of octahedral Co(II) derived from oxygen vacancies, improved the charge transfer in the spinel lattice while providing a new electron transfer channel from lattice Co(II)/Fe(II) to the surface of FeCo2O4. Simultaneously, strengthened the surface adsorption of HSO5− and increased the number of unpaired electrons, thus boosting the PMS activation performance. In addition, the influence of reaction parameters and water matrix were investigated. Finally, the degradation pathway of MNZ was proposed and the toxicity of intermediates was also assessed. This work is expected to facilitate the design and application of PMS/Co(II)-FCQDs/FNS system for decontaminating organic pollutants from wastewater.
Strain NB-1, which can efficiently degrade nitrobenzene, was identified as Pseudomonas frederiksbergensis. NB-1 was resistant to cold and alkali with the widest temperature (4-35 °C) and pH (5-11) ...adaptive range, compared with other reported nitrobenzene-degrading microorganisms. Based on the Haldane-Andrews model, the real maximum specific growth rate μ
m
', specific affinity a
A
, and inhibition coefficient K
i
were used in response surface methodology (RSM) simultaneously for the first time to guide NB-1 to treat nitrobenzene wastewater. According to the RSM model, the environmental factors (temperature, pH, salinity) corresponding to the optimal values of μ
m
', a
A
, and K
i
were determined. By comparing the specific growth rates corresponding to the optimal values of μ
m
', a
A
, and K
i
, respectively, the optimum growth conditions of NB-1 were determined under different nitrobenzene concentrations. The study of μ
m
', a
A
, and K
i
by RSM provided a new approach for a more accurate optimization of biological wastewater treatment conditions.
Phenanthrene, one of the polycyclic aromatic hydrocarbons, is stubborn and persistent and exists widely in petroleum-contaminated soil. Filamentous fungi are good assistants to bacterial transport, ...by hyphae passing through soil pores and reaching further positions. An isolated bacterial strain, from the contaminated soil of the coking plant, was identified as Diaphorobacter and named LW2, which could use phenanthrene as the only carbon source and energy for its growth. LW2 could degrade phenanthrene in a wide range of pH, temperature and initial concentration. When pH was 6 and 10, the removal rate of phenanthrene was 38.59% and 76.44%, respectively, and the removal rate of phenanthrene was 68.25% at 15 ℃. And LW2 could degrade 86.64% phenanthrene when the initial concentration was 100 mg L
−1
. The detection of DI-N-octyl phthalate, phthalic acid and p-hydroxybenzoic acid revealed that the strain LW2 metabolised phenanthrene through the phthalic acid pathway. Meanwhile, swimming and swarming test results suggested that LW2 was motile. The auxiliary effect of Pythium ultimum on LW2 migration was assessed. In the presence of Pythium ultimum, LW2 could migrate within the range of centimters by its mycelium, which was also observed by fluorescence microscopy. Meanwhile, the degradation ability of LW2 after the migration was also explored. The results proved that the migration process had no significant effect on its degradation ability, and LW2 still showed good phenanthrene metabolism ability. This study provides more possibilities for the bioremediation of phenanthrene-contaminated soil by screening the degradation bacteria and testing the effect of fungi on its migration.
AB OBJECTIVE: We aimed to investigate whether the efficacy and safety of clopidogrel plus aspirin vs aspirin alone were consistent between patients with and without intracranial arterial stenosis ...(ICAS), in the Clopidogrel in High-Risk Patients with Acute Non-disabling Cerebrovascular Events (CHANCE) trial.
We assessed the interaction of the treatment effects of the 2 antiplatelet therapies among patients with and without ICAS, identified by magnetic resonance angiography (MRA) in CHANCE (ClinicalTrials.gov identifier NCT00979589).
Overall, 1,089 patients with MRA images available in CHANCE were included in this subanalysis, 608 patients (55.8%) with ICAS and 481 (44.2%) without. Patients with ICAS had higher rates of recurrent stroke (12.5% vs 5.4%; p<0.0001) at 90 days than those without. But there was no statistically significant treatment by presence of ICAS interaction on either the primary outcome of any stroke (hazard ratio for clopidogrel plus aspirin vs aspirin alone: 0.79 0.47-1.32 vs 1.12 0.56-2.25; interaction p=0.522) or the safety outcome of any bleeding event (interaction p=0.277).
The results indicated higher rate of recurrent stroke in minor stroke or high-risk TIA patients with ICAS than in those without. However, there was no significant difference in the response to the 2 antiplatelet therapies between patients with and without ICAS in the CHANCE trial. Classification of evidence: This study provides Class II evidence that for patients with acute minor stroke or TIA with and without ICAS identified by MRA, clopidogrel plus aspirin is not significantly different than aspirin alone in preventing recurrent stroke.
To determine the relationship of glycated albumin (GA) and the recurrence of stroke in patients on either dual or single antiplatelet therapy.
The Clopidogrel in High-Risk Patients with Acute ...Nondisabling Cerebrovascular Events trial randomized minor ischemic stroke or TIA patients to antiplatelet therapy of clopidogrel plus aspirin or aspirin alone. A subgroup of 3,044 consecutive patients with baseline GA levels from 73 (64%) prespecified clinical sites was analyzed. Patients were categorized into 2 groups based on GA level of 15.5%, the cut point for development of diabetes. The primary outcome was stroke recurrence during 90-day follow-up. Cox proportional hazards models were used to assess the interaction of GA with randomized antiplatelet therapy on their risk of recurrent stroke.
Significant interaction of GA levels with the 2 antiplatelet therapy groups was found after adjustment for age, sex, and other conventional confounding factors (p = 0.009). The interaction remained consistent after further adjustment for history of diabetes (p = 0.010). In patients with lower GA level, stroke occurred in 5.5% of patients in the clopidogrel-aspirin group, and 12.7% in the aspirin group (adjusted hazard ratio HR 0.40; 95% confidence interval CI 0.26-0.61; p < 0.001). Furthermore, in patients with elevated GA level, stroke occurred in 9.2% of patients in the clopidogrel-aspirin group, and 11.4% in the aspirin group (adjusted HR 0.79; 95% CI 0.60-1.05; p = 0.103).
GA could be a potential biomarker to predict the effects of dual and single antiplatelet therapy in patients with minor stroke or TIA.
Genetic variants of ABCB1 may affect intestinal absorption of clopidogrel bisulfate. However, it is unclear whether ABCB1 polymorphisms are associated with clopidogrel efficacy for minor ischemic ...stroke or transient ischemic attack (TIA).
To investigate the association between ABCB1 polymorphisms and clopidogrel efficacy for minor stroke or TIA.
In this prespecified secondary analysis of the Clopidogrel in High-Risk Patients With Acute Nondisabling Cerebrovascular Events (CHANCE) randomized clinical trial, 3010 patients with minor stroke or TIA at 73 sites in China with experience in conducting genetic studies were included from October 1, 2009, to July 30, 2012. The analysis was conducted on March 20, 2018. Four single-nucleotide polymorphisms (ABCB1 -154T>C rs4148727, ABCB1 3435C>T rs1045642, CYP2C19*2 681G>A, rs4244285, and CYP2C19*3 636G>A, rs4986893) were genotyped among 2836 patients treated with clopidogrel plus aspirin (n = 1414) or aspirin alone (n = 1422). The association of ABCB1 genetic variants (-154 TC/CC and 3435 CT/TT) with clopidogrel efficacy was evaluated in the context of CYP2C19 status, another gene associated with clopidogrel efficacy.
Patients in the CHANCE trial were randomized to treatment with clopidogrel combined with aspirin or to aspirin alone.
Primary efficacy outcome was stroke recurrence after 3 months. The safety outcome was any bleeding risk after 3 months.
Among 2836 patients, the median age was 61.8 years (interquartile range, 54.4-71.1 years) and 1887 patients (66.5%) were male. A total of 2146 (75.7%) patients were carriers of ABCB1 -154 TC/CC (570 20.1%) or 3435 CT/TT (1851 65.3%) genotype. Clopidogrel plus aspirin treatment was associated with reduced risk of new stroke in patients with ABCB1 -154 TT and 3435 CC genotype (hazard ratio HR, 0.43; 95% CI, 0.26-0.71) but not in those with ABCB1 -154 TC/CC or 3435 CT/TT genotype (HR, 0.78; 95% CI, 0.60-1.03) compared with aspirin (P = .04 for interaction). A combined association of ABCB1 and CYP2C19 polymorphisms with new stroke was observed. The risk of bleeding for clopidogrel plus aspirin treatment was not associated with the ABCB1 genotypes (2.3% and 1.3% vs 1.9% and 2.2%; P = .25 for interaction in patients with or without ABCB1 -154 TC/CC or 3435 CT/TT genotype).
The ABCB1 polymorphism was associated with the reduced efficacy of clopidogrel plus aspirin treatment compared with aspirin among patients with minor ischemic stroke or TIA. Genetic polymorphism of ABCB1 should be considered when prescribing clopidogrel for these patients.
ClinicalTrials.gov identifier: NCT00979589.
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