Simulating the synergy of electron donors and different redox mediators on the anaerobic decolorization of azo dyes: Can AQDS-chitosan globules replace the traditional redox mediators?

ABSTRACT During aerobic degradation of naphthalene-2-sulfonate (2NS), Sphingomonas xenophaga strain BN6 produces redox mediators which significantly increase the ability of the strain to reduce azo dyes under anaerobic conditions. It was previously suggested that 1,2-dihydroxynaphthalene (1,2-DHN), which is an intermediate in the degradative pathway of 2NS, is the precursor of these redox mediators. In order to analyze the importance of the formation of 1,2-DHN, the dihydroxynaphthalene dioxygenase gene (nsaC) was disrupted by gene replacement. The resulting strain, strain AKE1, did not degrade 2NS to salicylate. After aerobic preincubation with 2NS, strain AKE1 exhibited much higher reduction capacities for azo dyes under anaerobic conditions than the wild-type strain exhibited. Several compounds were present in the culture supernatants which enhanced the ability of S. xenophaga BN6 to reduce azo dyes under anaerobic conditions. Two major redox mediators were purified from the culture supernatants, and they were identified by high-performance liquid chromatography-mass spectrometry and comparison with chemically synthesized standards as 4-amino-1,2-naphthoquinone and 4-ethanolamino-1,2-naphthoquinone.

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Immobilized Redox Mediators on Anion Exchange Resins and Their Role on the Reductive Decolorization of Azo Dyes

Environmental Science & Technology ◽

10.1021/es9027919 ◽

2010 ◽

Vol 44 (5) ◽

pp. 1747-1753 ◽

Cited By ~ 60

Author(s):

Francisco J. Cervantes ◽

Alberto Garcia-Espinosa ◽

M. Antonieta Moreno-Reynosa ◽

J. Rene Rangel-Mendez

Keyword(s):

Anion Exchange ◽

Azo Dyes ◽

Redox Mediators ◽

Anion Exchange Resins ◽

Exchange Resins ◽

Reductive Decolorization

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Microbial reductive dechlorination of trichloroethene to ethene with electrodes serving as electron donors without the external addition of redox mediators

Biotechnology and Bioengineering ◽

10.1002/bit.22234 ◽

2009 ◽

Vol 103 (1) ◽

pp. 85-91 ◽

Cited By ~ 102

Author(s):

Federico Aulenta ◽

Andrea Canosa ◽

Priscilla Reale ◽

Simona Rossetti ◽

Stefania Panero ◽

...

Keyword(s):

Reductive Dechlorination ◽

Electron Donors ◽

Redox Mediators ◽

Microbial Reductive Dechlorination

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Catalytic effects of different redox mediators on the reductive decolorization of azo dyes

Water Science & Technology ◽

10.2166/wst.2006.500 ◽

2006 ◽

Vol 54 (2) ◽

pp. 165-170 ◽

Cited By ~ 15

Author(s):

A.A. Encinas-Yocupicio ◽

E. Razo-Flores ◽

F. Sánchez-Díaz ◽

A.B. dos Santos ◽

J.A. Field ◽

...

Keyword(s):

Azo Dyes ◽

Granular Sludge ◽

Order Rate Constant ◽

Anaerobic Treatment ◽

Redox Mediator ◽

Redox Potentials ◽

Redox Mediators ◽

Direct Blue ◽

Reactive Orange ◽

Catalytic Effects

The catalytic effects of redox mediators, with distinct standard redox potentials (E′0), were evaluated on the first-order rate constant of decolorization (Kd) of recalcitrant azo dyes by an anaerobic granular sludge. The dyes studied included mono-azo (Reactive Orange 14, RO14), di-azo (Direct Blue 53, DB53), and tri-azo (Direct Blue 71, DB71) compounds. Toxicity and auto-catalytic aspects seemed to play a role in determining the rate of decolorization. Addition of riboflavin, anthraquinone-2,6-disulphonate (AQDS) or lawsone as a redox mediator, increased the Kd value for all dyes studied, although their impact varied in every case. Kd values were increased from 1.1-fold up to 3.8-fold depending on the redox mediator applied. Moreover, catalysts with moderately similar E′0 value caused distinct stimulation on the rate of decolorization. These results should be considered for selecting the proper redox mediator to be applied during the anaerobic treatment of textile wastewaters and effluents containing electron-withdrawing pollutants, such as nitro-aromatic and polychlorinated compounds.

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Seafood Processing Chitin Waste for Electricity Generation in a Microbial Fuel Cell Using Halotolerant Catalyst Oceanisphaera arctica YHY1

Sustainability ◽

10.3390/su13158508 ◽

2021 ◽

Vol 13 (15) ◽

pp. 8508

Author(s):

Ranjit Gurav ◽

Shashi Kant Bhatia ◽

Tae-Rim Choi ◽

Hyun-joong Kim ◽

Hong-Ju Lee ◽

...

Keyword(s):

Microbial Fuel Cells ◽

Electricity Generation ◽

Electron Donors ◽

Redox Mediators ◽

Processing Waste ◽

Electron Transfer Mechanism ◽

Chitin Degradation ◽

Membrane Bound ◽

Seafood Processing ◽

Optimum Salt Concentration

In this study, a newly isolated halotolerant strain Oceanisphaera arctica YHY1, capable of hydrolyzing seafood processing waste chitin biomass, is reported. Microbial fuel cells fed with 1% chitin and 40 g L−1 as the optimum salt concentration demonstrated stable electricity generation until 216 h (0.228 mA/cm2). N-acetyl-D-glucosamine (GlcNAc) was the main by-product in the chitin degradation, reaching a maximum concentration of 192.01 mg g−1 chitin at 120 h, whereas lactate, acetate, propionate, and butyrate were the major metabolites detected in the chitin degradation. O. arctica YHY1 utilized the produced GlcNAc, lactate, acetate, and propionate as the electron donors to generate the electric current. Cyclic voltammetry (CV) investigation revealed the participation of outer membrane-bound cytochromes, with extracellular redox mediators partly involved in the electron transfer mechanism. Furthermore, the changes in structural and functional groups in chitin after degradation were analyzed using FTIR and XRD. Therefore, the ability of O. arctica YHY1 to utilize waste chitin biomass under high salinities can be explored to treat seafood processing brine or high salt wastewater containing chitin with concurrent electricity generation.

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Chemical-Assisted Microbially Mediated Chromium (Cr) (VI) Reduction Under the Influence of Various Electron Donors, Redox Mediators, and Other Additives: An Outlook on Enhanced Cr(VI) Removal

Frontiers in Microbiology ◽

10.3389/fmicb.2020.619766 ◽

2021 ◽

Vol 11 ◽

Author(s):

Zeeshanur Rahman ◽

Lebin Thomas

Keyword(s):

Reduction Rate ◽

Reduction Process ◽

Electron Donors ◽

Main Process ◽

Redox Mediators ◽

Treatment Practices ◽

Inorganic Substances ◽

Comprehensive Information ◽

High Valence State ◽

Biological Organisms

Chromium (Cr) (VI) is a well-known toxin to all types of biological organisms. Over the past few decades, many investigators have employed numerous bioprocesses to neutralize the toxic effects of Cr(VI). One of the main process for its treatment is bioreduction into Cr(III). Key to this process is the ability of microbial enzymes, which facilitate the transfer of electrons into the high valence state of the metal that acts as an electron acceptor. Many underlying previous efforts have stressed on the use of different external organic and inorganic substances as electron donors to promote Cr(VI) reduction process by different microorganisms. The use of various redox mediators enabled electron transport facility for extracellular Cr(VI) reduction and accelerated the reaction. Also, many chemicals have employed diverse roles to improve the Cr(VI) reduction process in different microorganisms. The application of aforementioned materials at the contaminated systems has offered a variety of influence on Cr(VI) bioremediation by altering microbial community structures and functions and redox environment. The collective insights suggest that the knowledge of appropriate implementation of suitable nutrients can strongly inspire the Cr(VI) reduction rate and efficiency. However, a comprehensive information on such substances and their roles and biochemical pathways in different microorganisms remains elusive. In this regard, our review sheds light on the contributions of various chemicals as electron donors, redox mediators, cofactors, etc., on microbial Cr(VI) reduction for enhanced treatment practices.

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