Discovery of an Inducible Toluene Monooxygenase That Cooxidizes 1,4-Dioxane and 1,1-Dichloroethylene in Propanotrophic Azoarcus sp. Strain DD4

ABSTRACT Cometabolic degradation plays a prominent role in bioremediation of commingled groundwater contamination (e.g., chlorinated solvents and the solvent stabilizer 1,4-dioxane [dioxane]). In this study, we untangled the diversity and catalytic functions of multicomponent monooxygenases in Azoarcus sp. strain DD4, a Gram-negative propanotroph that is effective in degrading dioxane and 1,1-dichloroethylene (1,1-DCE). Using a combination of knockout mutagenesis and heterologous expression, a toluene monooxygenase (MO) encoded by the tmoABCDEF gene cluster was unequivocally proved to be the key enzyme responsible for the cometabolism of both dioxane and 1,1-DCE. Interestingly, in addition to utilizing toluene as a primary substrate, this toluene MO can also oxidize propane into 1-propanol. Expression of this toluene MO in DD4 appears inducible by both substrates (toluene and propane) and their primary hydroxylation products (m-cresol, p-cresol, and 1-propanol). These findings coherently explain why DD4 can grow on propane and express toluene MO for active cooxidation of dioxane and 1,1-DCE. Furthermore, upregulation of tmo transcription by 1-propanol underlines the implication potential of using 1-propanol as an alternative auxiliary substrate for DD4 bioaugmentation. The discovery of this toluene MO in DD4 and its degradation and induction versatility can lead to broad applications, spanning from environmental remediation and water treatment to biocatalysis in green chemistry. IMPORTANCE Toluene MOs have been well recognized given their robust abilities to degrade a variety of environmental pollutants. Built upon previous research efforts, this study ascertained the untapped capability of a toluene MO in DD4 for effective cooxidation of dioxane and 1,1-DCE, two of the most prevailing yet challenging groundwater contaminants. This report also aligns the induction of a toluene MO with nontoxic and commercially accessible chemicals (e.g., propane and 1-propanol), extending its implications in the field of environmental microbiology and beyond.

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Recent Trends in Development of Nanomaterials Based Green Analytical Methods for Environmental Remediation

Current Analytical Chemistry ◽

10.2174/1573411016666200319100707 ◽

2020 ◽

Vol 16 ◽

Cited By ~ 3

Author(s):

Sidra Amin ◽

Amber R. Solangi ◽

Dilawar Hassan ◽

Nadir Hussain ◽

Jamil Ahmed ◽

...

Keyword(s):

Optical Sensors ◽

Environmental Remediation ◽

Environmental Chemistry ◽

Limit Of Detection ◽

Environmental Pollutants ◽

Toxic Metal ◽

Electrochemical Analysis ◽

Good Choice ◽

Nano Materials ◽

Limit Of Quantification

Background: In recent years, the occurrence and fate of environmental pollutants has been recognized as one of the emerging issues in environmental chemistry. A survey documented about a wide variety of these pollutants, which are often detected in our environment and these are major cause of shortened life spans and the global warming. These pollutants include toxic metal, pesticides, fertilizers, drugs and dyes released into soil and major water bodies. The presence of these contaminants causes major disturbance in eco-system’s balance. To tackle these issues many technological improvements are made to detect minute contaminations. The latest issue being answered by the scientists is the use of green nano materials as sensors which are economical, instant and give much better results at low concentrations and can be used for the field measurements resulting in no dangerous by-product that could lead to more environmental contamination. Nano materials are known for their wide band gap, enhanced physical and optical properties with option of tuneablity as per need, by optimizing certain parameters. They are proved to be good choice for analytical/optical sensors with high sensitivity. Objective: This review holds information about multiple methods that use green nanomaterials for the analytical assessment of environmental pollutants. UV-Vis spectrophotometry and electrochemical analysis using green and reproducible nanomaterials are the major focus of this review article. To date, there are number of spectrophotometric and electro chemical methods available that have been used for the detection of environmental pollutants such as toxic metals, pesticides and dyes. Conclusion: The use of nanomaterials can drastically change the detection limits due to having large surface area, strong catalytic properties, and tunable possibility. With the use of nano materials, lower than the marked limit of detection and limit of quantification were seen when compared with previously reported work. The used nano-materials could be washed, dried, and reused, which makes the methods more proficient, cost effective and environmentally friendly.

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A Microcosm Treatability Study for Evaluating Wood Mulch-Based Amendments as Electron Donors for Trichloroethene (TCE) Reductive Dechlorination

Water ◽

10.3390/w13141949 ◽

2021 ◽

Vol 13 (14) ◽

pp. 1949

Author(s):

Edoardo Masut ◽

Alessandro Battaglia ◽

Luca Ferioli ◽

Anna Legnani ◽

Carolina Cruz Viggi ◽

...

Keyword(s):

Electron Donor ◽

Environmental Sustainability ◽

Reductive Dechlorination ◽

Environmental Remediation ◽

Low Cost ◽

Chlorinated Solvents ◽

Electron Donors ◽

Chlorinated Ethenes ◽

Dehalococcoides Mccartyi ◽

Wood Mulch

In this study, wood mulch-based amendments were tested in a bench-scale microcosm experiment in order to assess the treatability of saturated soils and groundwater from an industrial site contaminated by chlorinated ethenes. Wood mulch was tested alone as the only electron donor in order to assess its potential for stimulating the biological reductive dechlorination. It was also tested in combination with millimetric iron filings in order to assess the ability of the additive to accelerate/improve the bioremediation process. The efficacy of the selected amendments was compared with that of unamended control microcosms. The results demonstrated that wood mulch is an effective natural and low-cost electron donor to stimulate the complete reductive dechlorination of chlorinated solvents to ethene. Being a side-product of the wood industry, mulch can be used in environmental remediation, an approach which perfectly fits the principles of circular economy and addresses the compelling needs of a sustainable and low environmental impact remediation. The efficacy of mulch was further improved by the co-presence of iron filings, which accelerated the conversion of vinyl chloride into the ethene by increasing the H2 availability rather than by catalyzing the direct abiotic dechlorination of contaminants. Chemical analyses were corroborated by biomolecular assays, which confirmed the stimulatory effect of the selected amendments on the abundance of Dehalococcoides mccartyi and related reductive dehalogenase genes. Overall, this paper further highlights the application potential and environmental sustainability of wood mulch-based amendments as low-cost electron donors for the biological treatment of chlorinated ethenes.

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Structural Basis for Substrate Specificity in ArnB. A Key Enzyme in the Polymyxin Resistance Pathway of Gram-Negative Bacteria

Biochemistry ◽

10.1021/bi4015677 ◽

2014 ◽

Vol 53 (4) ◽

pp. 796-805 ◽

Cited By ~ 11

Author(s):

Myeongseon Lee ◽

Marcelo C. Sousa

Keyword(s):

Substrate Specificity ◽

Structural Basis ◽

Gram Negative Bacteria ◽

Gram Negative ◽

Resistance Pathway ◽

Key Enzyme

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Diverse allosteric and catalytic functions of tetrameric d-lactate dehydrogenases from three Gram-negative bacteria

AMB Express ◽

10.1186/s13568-014-0076-1 ◽

2014 ◽

Vol 4 (1) ◽

Cited By ~ 8

Author(s):

Nayuta Furukawa ◽

Akimasa Miyanaga ◽

Misato Togawa ◽

Masahiro Nakajima ◽

Hayao Taguchi

Keyword(s):

Gram Negative Bacteria ◽

Gram Negative ◽

Lactate Dehydrogenases ◽

Catalytic Functions

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INVESTIGATION OF REMOVAL OF HEXAVALENT CHROMIUM AND DIVALENT COBALT FROM AQUEOUS SOLUTIONS BY ORGANO-MONTMORILLONITE SUPPORTED IRON NANOPARTICLES

EUREKA Physics and Engineering ◽

10.21303/2461-4262.2016.00163 ◽

2016 ◽

Vol 5 ◽

pp. 81-88 ◽

Cited By ~ 1

Author(s):

Viktoriia Prus ◽

Nataliya Zhdanyuk

Keyword(s):

Environmental Remediation ◽

Iron Nanoparticles ◽

Removal Rate ◽

Environmental Pollutants ◽

Zero Valent Iron ◽

Hexadecyltrimethylammonium Bromide ◽

X Ray Diffraction ◽

X Ray ◽

Nanoscale Zero Valent Iron ◽

Supported Iron

A new class of nanoscale zero-valent iron particles supported on natural montmorillonite and organo-montmorillonite were synthesized and the feasibility for the removal of and was examined through laboratory batch test. The X – ray diffraction (XRD) and Fourier Transform Infrared spectrum (FTIR) investigation has been applied for determination of the particle size and mechanism of remediation process. The aim of this study was to enhance the reduction of persistent environmental pollutants difficult to degrade by immobilization of nanoscale zero-valent iron on an organo-montmorillonite. Batch experiments indicated that the reduction of both and was much greater with organo-montmorillonite supported iron nanoparticles reaching removal rate up to 98.5% and 95.6% respectively at the initial metal concentrations of 50 mg/L. Iron and crystalline iron oxide were detected by X-ray diffraction patterns. In the FTIR spectrum, CH2 groups were found in iron nanoparticles supported on hexadecyltrimethylammonium bromide modified montmorillonite (HDTMA-Mont/nZVI) particles but were significantly weakened in comparison with the spectrum of hexadecyl trimethylammonium bromide (HDTMA). Other factor that affects the efficiency of heavy metals removal such as pH values was also investigated. The obtained data and review of the current literature have given the opportunity to figure out the mechanisms of and removal which may thus promote the industrial application of nZVI technique in environmental remediation by changing the hydrophilic – hydrophobic properties of source systems.

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Lignin Biopolymer for the Synthesis of Iron Nanoparticles and the Composite Applied for the Removal of Methylene Blue

Polymers ◽

10.3390/polym13213847 ◽

2021 ◽

Vol 13 (21) ◽

pp. 3847

Author(s):

Fang-Yi Peng ◽

Pei-Wen Wang ◽

Weisheng Liao ◽

Ing-Song Yu

Keyword(s):

Methylene Blue ◽

Aqueous Solutions ◽

Environmental Remediation ◽

Present Method ◽

Room Temperature ◽

Iron Nanoparticles ◽

Reduction Method ◽

Environmental Pollutants ◽

Borohydride Reduction ◽

Natural Polymer

In the current study, lignin, an abundant natural polymer, was dissolved in ethylene glycol and acidic H2O to form nanoscale lignin. Then, zero-valent iron (ZVI) nanoparticles were synthesized in nanoscale lignin, producing a nZVI/n-lignin composite, via the borohydride reduction method. The use of nZVI/n-lignin for environmental remediation was tested by the removal of methylene blue in aqueous solutions at room temperature. The nZVI/n-lignin composite achieved a higher methylene blue removal ratio than that achieved by traditional nZVIs. Moreover, its excellent dispersibility in water and stability against oxidation in the air were observed. The functions of the nanoscale lignin in the composite material are (1) prevention of further growth and aggregation of the nZVI nanoparticles, (2) protection of nZVI from serious oxidation by H2O/O2, and (3) allowing better dispersibility of nZVI in aqueous solutions. These three functions are important for the field applications of nZVI/n-lignin, namely, to travel long distances before making contact with environmental pollutants. The present method for producing nZVI/n-lignin is straightforward, and the combination of nZVI and lignin is an efficient and environmentally friendly material for environmental applications.

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Novel High Efficiency Layered Oxide Photocatalyst Li2SnO3 for Rhodamine B and Tetracycline Degradation

Catalysts ◽

10.3390/catal9090712 ◽

2019 ◽

Vol 9 (9) ◽

pp. 712 ◽

Cited By ~ 2

Author(s):

Yuanyuan Li ◽

Meijun Wu ◽

Dingfeng Yang ◽

Hanlu Zeng ◽

Tao Zhang ◽

...

Keyword(s):

Electron Microscopy ◽

Rhodamine B ◽

Environmental Remediation ◽

Photocatalytic Oxidation ◽

High Efficiency ◽

Uv Light ◽

Environmental Pollutants ◽

Active Species ◽

Optical Measurements ◽

Layered Crystal

The use of a layered Li2SnO3 material as an efficient photocatalyst for the degradation of environmental pollutants (Rhodamine B and tetracycline) was investigated. The structure and morphology of the material were characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy. Optical measurements demonstrated that Li2SnO3 was a UV-light-responsive material with a band gap of 3.71 eV. The maximum kinetic rate constants of photocatalytic degradation of Rhodamine B and tetracycline solutions were 0.0155 min−1 and 0.0406 min−1 · L/mg, respectively, when exposed to UV-light irradiation within 120 min. Trapping experiments demonstrated that holes ( h + ) , hydroxyl radical ( · O H ) and superoxide radical ( · O 2 − ) were the dominant active species during the degradation of Rhodamine B and tetracycline. Theoretical band structure calculations revealed that Li2SnO3 was a direct gap semiconductor with a large m h * / m e * value (4.7) near the band edge. Partial charge density near the top of the valence band indicated that the photocatalytic oxidation reaction occurred largely on the O-2p states. The excellent photocatalytic performance was attributed to the synergistic effect of the layered crystal structure and large m h * / m e * . This work represents an important contribution to the design and optimization of efficient oxide photocatalysts with layered crystal structures for environmental remediation.

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Iron-Dependent Enzyme Catalyzes the Initial Step in Biodegradation of N-Nitroglycine by Variovorax sp. Strain JS1663

Applied and Environmental Microbiology ◽

10.1128/aem.00457-17 ◽

2017 ◽

Vol 83 (15) ◽

Cited By ~ 3

Author(s):

Kristina M. Mahan ◽

Hangping Zheng ◽

Tekle T. Fida ◽

Ronald J. Parry ◽

David E. Graham ◽

...

Keyword(s):

Environmental Remediation ◽

Single Gene ◽

Soil Bacterium ◽

Growth Substrate ◽

Elimination Reaction ◽

Natural Ecosystems ◽

Gram Negative ◽

Content Type ◽

Biodegradation Pathway ◽

Military Facilities

ABSTRACT Nitramines are key constituents of most of the explosives currently in use and consequently contaminate soil and groundwater at many military facilities around the world. Toxicity from nitramine contamination poses a health risk to plants and animals. Thus, understanding how nitramines are biodegraded is critical to environmental remediation. The biodegradation of synthetic nitramine compounds such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has been studied for decades, but little is known about the catabolism of naturally produced nitramine compounds. In this study, we report the isolation of a soil bacterium, Variovorax sp. strain JS1663, that degrades N-nitroglycine (NNG), a naturally produced nitramine, and the key enzyme involved in its catabolism. Variovorax sp. JS1663 is a Gram-negative, non-spore-forming motile bacterium isolated from activated sludge based on its ability to use NNG as a sole growth substrate under aerobic conditions. A single gene (nnlA) encodes an iron-dependent enzyme that releases nitrite from NNG through a proposed β-elimination reaction. Bioinformatics analysis of the amino acid sequence of NNG lyase identified a PAS (Per-Arnt-Sim) domain. PAS domains can be associated with heme cofactors and function as signal sensors in signaling proteins. This is the first instance of a PAS domain present in a denitration enzyme. The NNG biodegradation pathway should provide the basis for the identification of other enzymes that cleave the N—N bond and facilitate the development of enzymes to cleave similar bonds in RDX, nitroguanidine, and other nitramine explosives. IMPORTANCE The production of antibiotics and other allelopathic chemicals is a major aspect of chemical ecology. The biodegradation of such chemicals can play an important ecological role in mitigating or eliminating the effects of such compounds. N-Nitroglycine (NNG) is produced by the Gram-positive filamentous soil bacterium Streptomyces noursei. This study reports the isolation of a Gram-negative soil bacterium, Variovorax sp. strain JS1663, that is able to use NNG as a sole growth substrate. The proposed degradation pathway occurs via a β-elimination reaction that releases nitrite from NNG. The novel NNG lyase requires iron(II) for activity. The identification of a novel enzyme and catabolic pathway provides evidence of a substantial and underappreciated flux of the antibiotic in natural ecosystems. Understanding the NNG biodegradation pathway will help identify other enzymes that cleave the N—N bond and facilitate the development of enzymes to cleave similar bonds in synthetic nitramine explosives.

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Cometabolic Degradation of Dibenzofuran by Biphenyl-CultivatedRalstonia sp. Strain SBUG 290

Applied and Environmental Microbiology ◽

10.1128/aem.66.10.4528-4531.2000 ◽

2000 ◽

Vol 66 (10) ◽

pp. 4528-4531 ◽

Cited By ~ 40

Author(s):

Dörte Becher ◽

Michael Specht ◽

Elke Hammer ◽

Wittko Francke ◽

Frieder Schauer

Keyword(s):

Salicylic Acid ◽

Degradation Mechanism ◽

Enoic Acid ◽

Negative Bacterium ◽

Gram Negative ◽

Cometabolic Degradation ◽

Lateral Dioxygenation

ABSTRACT Cells of the gram-negative bacterium Ralstonia sp. strain SBUG 290 grown in the presence of biphenyl are able to cooxidize dibenzofuran which has been 1,2-hydroxylated. Meta cleavage of the 1,2-dihydroxydibenzofuran between carbon atoms 1 and 9b produced 2-hydroxy-4-(3′-oxo-3′H-benzofuran-2′-yliden)but-2-enoic acid, which was degraded completely via salicylic acid. The presence of these intermediates indicates a degradation mechanism for dibenzofuran via lateral dioxygenation by Ralstonia sp. strain SBUG 290.

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