Biological Reduction Process Research Articles

Transcriptome deciphered the mechanisms of iron facilitating enzyme-mediated ciprofloxacin biodegradation and regulating antibiotic resistance gene dissemination through inducing genes expression

Refractory chemically synthesized quinolones are frequently detected in aquatic environments, and their degradation via biological systems presents substantial challenges, which includes obstacles in undergoing biological transformation, residual toxicity, the enrichment and dissemination of antibiotic resistance genes (ARGs) induced by quinolones. Various forms of iron, including zero-valent iron (ZVI), Fe (II), and Fe (III), were employed to enhance the biodegradation of quinolones and associated environmental risks control in toxicity-tolerated hydrolysis acidification (HA) system in this research. Iron addition significantly improves ciprofloxacin (CIP) removal (22.8% to 41.28% increase) through improving activity of enzymes, especially for the identified dehydrogenases via meta-transcriptomic sequencing. Regarding the risks associated with ARGs and their dissemination, ZVI and Fe(Ⅱ) exhibit positive effects, while Fe(Ⅲ) has an inverse effect. The minimized residual CIP contributes to the reduction of reactive oxygen species (ROS) responsiveness and cellular membrane permeability, thereby decreasing the risks of ARGs dissemination in iron-added systems. However, the enrichment of Fe(Ⅲ) reduction bacteria in Fe(Ⅲ)-added HA systems was speculated to led to increased ARGs dissemination by generating additional ROS and causing cell damage during the Fe(Ⅲ) biological reduction process. Changes in relevant gene expression for ARG conjunction, ROS generation, cell membrane permeability, and DNA repair, as observed through qPCR and meta-transcriptomic sequencing, support these conclusions. The findings suggest that ZVI and Fe(Ⅱ) contribute to reducing risks associated with ARGs and their dissemination in the biological system, which could be prioritized. This research also contributes insights into efficient quinolone removal and environmental risk migrating simultaneously through iron-enhanced biodegradation processes.

Progresses in the NOX Elimination Using Zeolite Under Low‐Temperature Ammonia‐Based Selective Catalytic Reduction—A Review

The chemical absorption biological reduction process gained profound attention in NOx removal. Treatments for NOx are done popularly using NH3 in selective catalytic reduction (SCR), and deNOx is greatly influenced by catalyst. In recent years, zeolites have been widely explored in ammonia‐selective catalytic reduction (NH3‐SCR) under low‐temperature windows. Different methods were employed to juxtapose the performances of zeolite catalysts with denitrification and NH3‐SCR. In this NH3‐SCR reaction, the zeolite catalyst’s sulfur and water poisoning effects were also investigated. The negatives of the low‐temperature NH3‐SCR reactions were demonstrated by using different methods. Ideally, this audit will set upon essential comprehension of the SCR response on zeolite catalysts and clear the way for future exploration to accomplish reasonable applications. The current review provides a new strategy to enhance the removal of NOx and reveals the fundamental effects of different types of sustainable catalysts for the environment. Further, the perspective of the economic aspects of each catalyst is also examined.

Bacterial mineralization of chromium-copper spinel with highly performance in electroplating effluent

Cr (VI) contamination has posed severe challenges to water quality, food safety, and land resources. Microbial reduction of Cr(VI) to Cr(III) has drawn considerable attention due to its low cost and environmental friendliness. However, recent reports have shown that Cr(VI) generates highly migratable organo-Cr(III) rather than stable inorganic chromium minerals during the biological reduction process. In this work, it was reported for the first time that spinel structure CuCr2O4 was formed by Bacillus cereus in Cr biomineralization process. Different from known biomineralization models (biologically controlled mineralization and biologically induced mineralization), the chromium-copper minerals here appeared as specialized minerals with extracellular distribution. In view of this, a possible mechanism of biologically secretory mineralization was proposed. In addition, Bacillus cereus demonstrated a high conversion ability in the treatment of electroplating wastewater. The Cr(VI) removal percentage reached 99.7%, which satisfied the Chinese emission standard of pollutants for electroplating (GB 21,900–2008), indicating its application potential. Altogether, our work elucidated a bacterial chromium spinel mineralization pathway and evaluated the potential of this system for application in actual wastewater, opening a new avenue in the field of chromium pollution treatment and control.

Nitrate removal during Fe(III) bio-reduction in microbial-mediated iron redox cycling systems

Abstract Fe(III) bio-reduction provides a prospect of applying the iron redox cycle to nitrate remediation in the aquatic environment. The objective of this study was to realize multiple nitrate removals in the system containing Shewanella oneidensis MR-1 (S. oneidensis MR-1) and ferrihydrite or magnetite. The results showed that with three periods of 30 mg·L−1 NO3−-N addition, all nitrate reduction was completed within 170 h. In the first period (0–30 h) of nitrate addition, the main contribution of nitrate removal was due to the biological reduction process by S. oneidensis MR-1, accompanied by the reduction of Fe(III). During the second (45–90 h) and third periods (100–170 h) of nitrate addition, oxidation of biogenic Fe(II) coupled with the reduction of nitrate took place. This redox reaction resulted in the production of gaseous nitrogen of 47.33% and 16.8% for ferrihydrite/S. oneidensis MR-1 and magnetite/S. oneidensis MR-1 systems, respectively. In addition, nitrite, as an intermediate product, accumulated and negatively affected nitrate removal after the third addition of nitrate. By comparing the patterns of X-ray diffraction of the iron minerals before and after the bio-reduction, it was found that ferrihydrite was transformed into magnetite, while magnetite kept its original crystal form.

Making good use of methane to remove oxidized contaminants from wastewater

Being an energetic fuel, methane is able to support microbial growth and drive the reduction of various electron acceptors. These acceptors include a broad range of oxidized contaminants (e.g., nitrate, nitrite, perchlorate, bromate, selenate, chromate, antimonate and vanadate) that are ubiquitously detected in water environments and pose threats to human and ecological health. Using methane as electron donor to biologically reduce these contaminants into nontoxic forms is a promising solution to remediate polluted water, considering that methane is a widely available and inexpensive electron donor. The understanding of methane-based biological reduction processes and the responsible microorganisms has grown in the past decade. This review summarizes the fundamentals of metabolic pathways and microorganisms mediating microbial methane oxidation. Experimental demonstrations of methane as an electron donor to remove oxidized contaminants are summarized, compared, and evaluated. Finally, the review identifies opportunities and unsolved questions that deserve future explorations for broadening understanding of methane oxidation and promoting its practical applications.

Promoting mechanism of electronic shuttle for bioavailability of Fe(III) oxide and its environmental significance

Abstract The biological reduction process of Fe(III) not only strongly affects the circulation of C, N, O, P and other elements in the environment, but also plays an important role in the transformation and degradation of organic and inorganic pollutants. Most Fe(III) oxides existing in nature have low bioavailability due to their poor solubility or strongly crystalline form with stable chemical properties. Addition of a substance having redox activity can form an electron shuttle cycle between Fe(III) oxide and the microorganism, which can not only enhance the bioavailability of Fe(III) and accelerate electron transfer, but also improve the removal efficiency of contaminants. This paper compares and analyzes several common redox active substances, for their promoting effect and limiting factors of Fe(III) bioavailability. Moreover, the mechanism by which the electron shuttle promotes the bioavailability of Fe(III) oxide is discussed. This review demonstrates that the electron shuttle promotes the Fe(III) bioreaction process for the degradation and removal of heavy metals, polycyclic aromatic hydrocarbons, azo dyes and other pollutants, which is of great environmental significance.

A New Concept of Promoting Nitrate Reduction in Surface Waters: Simultaneous Supplement of Denitrifiers, Electron Donor Pool, and Electron Mediators.

The efficiency of biological nitrate reduction depends on the community composition of microorganisms, the electron donor pool, and the electron mediators participating in the biological reduction process. This study aims at creating an in situ system comprising of denitrifiers, electron donors, and electron mediators to reduce nitrate in surface waters. The ubiquitous periphytic biofilm in waters was employed to promote in situ nitrate reduction in the presence of titanium dioxide (TiO2) nanoparticles (NPs). The nitrate removal rate in the periphytic biofilm and TiO2 NPs system was significantly higher than the control (only periphytic biofilm or TiO2 NPs). TiO2 NPs optimized the community composition of periphytic biofilm for nitrate reduction by increasing the relative abundance of four dominant denitrifying bacteria. Periphytic biofilm showed a substantial increase in extracellular polymeric substance, especially the humic acid and protein content, due to the presence of TiO2 NPs. The synergistic action of humic acid, protein, denitrifying bacteria of the periphytic biofilm, and TiO2 NPs contributed to 80% of the nitrate reduction. The protein and humic acid, acting as electron mediators, facilitated the transfer of exogenous electrons from photoexcited TiO2 NPs to periphytic biofilm containing denitrifiers, which enhanced nitrate reduction in surface waters.

Biochemical processes in soil and groundwater contaminated by leachates from municipal landfills (Mini review)

Abstract World clean water deficit grows by increasing pollution on the planet. Landfill of solid domestic waste is one of the most important sources of pollution, where the leachate seeping through soil, gets into the soil and groundwater. Area of landfills of solid household waste, reaches tens of hectares and the mass of waste reaches millions of tones. The specificity of the leachate is the high content of soluble organic substances, providing reduction conditions in contaminated soil and groundwater. Reduction environment is defines biogeochemical processes under landfills with the participation of: ammonium, iron, manganese, bicarbonate, sulfate, methane. The main processes in polluted soil stream are including: biological degradation of organic matter and a variety of biological and abiotic processes. Wide discrimination of the most diverse groups of microorganisms in the polluted leachate is occurs, overlay neighboring redox zones. Microbial population is identifies specific redox zones more contaminated leachate nucleus than on the borders of the leachate with oxygen-enriched by the background thread. Biological reduction processes in the leachate are developing at different speeds: fast evolving and denitrification reduction of iron, slow – methanogenesis.

Prediction and inhibition of the N2O accumulation in the BioDeNO x process for NO x removal from flue gas.

BioDeNO x process, which combines the advantages of the chemical absorption and biological reduction processes, is regarded as a promising candidate for NO removal from the flue gas. In the BioDeNO x , N2O was accumulated in the process of the biological reduction of FeII(EDTA)-NO. In this work, the pathway of the FeII(EDTA)-NO reduction was investigated and a mathematic model was developed to evaluate and predict the accumulation of N2O. Furthermore, parametric tests such as the effects of the C/N ratio (molar ratio of carbon/nitrogen), electron donor, and sulfite concentrations on N2O accumulation were investigated. Experimental results revealed that N2O accumulation was inhibited with a high C/N ratio (2.4), sufficient electron donor, and a low sulfite concentration. In addition, compared with the inorganic electron donor (FeII(EDTA)), the organic electron donor (glucose) was beneficial for microorganism metabolism and N2O accumulation inhibition. This work will provide significant insight into the inhibition of N2O accumulation during the operation of BioDeNO x and advance this novel process for the industrial application.

Application of gas diffusion biocathode in microbial electrosynthesis from carbon dioxide.

Microbial catalysis of carbon dioxide (CO2) reduction to multi-carbon compounds at the cathode is a highly attractive application of microbial electrosynthesis (MES). The microbes reduce CO2 by either taking the electrons or reducing the equivalents produced at the cathode. While using gaseous CO2 as the carbon source, the biological reduction process depends on the dissolution and mass transfer of CO2 in the electrolyte. In order to deal with this issue, a gas diffusion electrode (GDE) was investigated by feeding CO2 through the GDE into the MES reactor for its reduction at the biocathode. A combination of the catalyst layer (porous activated carbon and Teflon binder) and the hydrophobic gas diffusion layer (GDL) creates a three-phase interface at the electrode. So, CO2 and reducing equivalents will be available to the biocatalyst on the cathode surface. An enriched inoculum consisting of acetogenic bacteria, prepared from an anaerobic sludge, was used as a biocatalyst. The cathode potential was maintained at -1.1V vs Ag/AgCl to facilitate direct and/or hydrogen-mediated CO2 reduction. Bioelectrochemical CO2 reduction mainly produced acetate but also extended the products to ethanol and butyrate. Average acetate production rates of 32 and 61mg/L/day, respectively, with 20 and 80% CO2 gas mixture feed were achieved with 10cm2 of GDE. The maximum acetate production rate remained 238mg/L/day for 20% CO2 gas mixture. In conclusion, a gas diffusion biocathode supported bioelectrochemical CO2 reduction with enhanced mass transfer rate at continuous supply of gaseous CO2. Graphical abstract ᅟ.

Catalytic Application of Biogenic Platinum Nanoparticles for the Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol

Pt catalysts and Co doped Pt catalysts with TiO2 as the support were prepared by the sol immobilization method based on biological synthesis process, whereby Pt nanoparticles (PtNPs) were reduced from Na2PtCl4 using Cacumen Platycladi extract (CPE). The catalytic performance of the catalysts was studied using hydrogenation of cinnamaldehyde as the model reaction. For comparison, Co doped Pt/catalysts were also prepared by traditional impregnation method, TEM observation, and XRD measurement were carried out to characterize the catalysts. The effects of different Pt loadings and Co doping amounts were investigated. The results showed that the PtNPs could be well dispersed onto the TiO2 support with narrow size distribution between 4 and 6 nm. 1.0% was observed as the optimal Pt loading amount in our experiments showing a cinnamaldehyde conversion of 73.3% with 68.8% selectivity to cinnamyl alcohol. A proper Co doping amount was also essential to the catalytic performance of the prepared Pt/catalysts as well as a favorable for the reaction process, 1.0% doping amount showed the best activity in which a 70.4% conversion and 88.3% selectivity was achieved. Recyclability tests carried out revealed that the 1.0 Co–1.0 Pt/TiO2 catalysts possessed possessing good durability. In this work, Co-Pt/TiO2 catalysts prepared by the sol immobilization method based on biological reduction process, showed better selectivity than that from traditional impregnation method.

Chemical and Biological Reduction of PCE by Pneumatic Fracturing and Injection of ZVI in Saprolite

AbstractThis article presents a case study of the source‐area treatment of tetrachloroethene (PCE) in a low‐permeability formation using zero‐valent iron (ZVI). Evidence of the stimulation of biological reduction processes within the treatment zone occurred. Pneumatic fracturing and injection of microscale ZVI slurry in the overburden and weathered bedrock zones was performed at a commercial brownfields redevelopment site in Maryland. A 20,000‐square‐foot source area impacted with PCE at concentrations greater than 15,000 µg/L was treated at depths ranging from 10 to 70 feet bgs. An average ZVI dosage of 0.0024 iron‐to‐soil mass ratio within the overburden zone led to a 75 percent decrease in PCE mass in less than one year. For the weathered bedrock zone, an average 0.0045 iron‐to‐soil mass ratio resulted in a 92 percent decrease in PCE mass during the same period. The reducing environment and hydrogen generated by the ZVI may have stimulated Dehalobacter populations, as evidenced by concentrations up to 104 cells per milliliter measured within the treatment area despite a groundwater pH as high as 9. The biological reductive dechlorination of the chlorinated ethenes explains the temporary increase in trichloroethene and cis‐1,2‐dichloroethene concentrations. © 2013 Wiley Periodicals, Inc.

ChemInform Abstract: The Coordination Chemistry of Organo‐Hydride Donors: New Prospects for Efficient Multi‐Electron Reduction

AbstractReview: 432 refs.

The coordination chemistry of organo-hydride donors: new prospects for efficient multi-electron reduction

In biological reduction processes the dihydronicotinamides NAD(P)H often transfer hydride to an unsaturated substrate bound within an enzyme active site. In many cases, metal ions in the active site bind, polarize and thereby activate the substrate to direct attack by hydride from NAD(P)H cofactor. This review looks more widely at the metal coordination chemistry of organic donors of hydride ion--organo-hydrides--such as dihydronicotinamides, other dihydropyridines including Hantzsch's ester and dihydroacridine derivatives, those derived from five-membered heterocycles including the benzimidazolines and benzoxazolines, and all-aliphatic hydride donors such as hexadiene and hexadienyl anion derivatives. The hydride donor properties--hydricities--of organo-hydrides and how these are affected by metal ions are discussed. The coordination chemistry of organo-hydrides is critically surveyed and the use of metal-organo-hydride systems in electrochemically-, photochemically- and chemically-driven reductions of unsaturated organic and inorganic (e.g. carbon dioxide) substrates is highlighted. The sustainable electrocatalytic, photochemical or chemical regeneration of organo-hydrides such as NAD(P)H, including for driving enzyme-catalysed reactions, is summarised and opportunities for development are indicated. Finally, new prospects are identified for metal-organo-hydride systems as catalysts for organic transformations involving 'hydride-borrowing' and for sustainable multi-electron reductions of unsaturated organic and inorganic substrates directly driven by electricity or light or by renewable reductants such as formate/formic acid.

Reduction of Fe(III)EDTA− in a NOx scrubbing solution by magnetic Fe3O4–chitosan microspheres immobilized mixed culture of iron-reducing bacteria

Magnetic Fe3O4–chitosan microspheres were prepared by co-precipitating of Fe2+ and Fe3+ ions with NaOH in the presence of chitosan. The saturated magnetization of the resulting material was 20.0emu/g. Then these magnetic microspheres were employed to immobilize iron-reducing bacteria to improve the biological reduction of Fe(III)EDTA−, which was one of the key steps in nitrogen oxides (NOx) removal by the integrated chemical absorption–biological reduction process. The immobilized bacteria performed well on Fe(III)EDTA− reduction than free bacteria, even under unfavorable pH and temperatures. Furthermore, the effects of NO2-,NO3-,SO3-, and S2−, the potential inhibition compounds in the scrubber solution, on the reduction of Fe(III)EDTA− by the immobilized and free bacteria were also studied.

Production of Nano Silver Sol Particle by Biological Reduction Process

Article Production of Nano Silver Sol Particle by Biological Reduction Process was published on December 1, 2011 in the journal Journal for Manufacturing Science and Production (volume 11, issue 1-3).

Enhanced biological removal of NOx from flue gas in a biofilter by Fe(II)Cit/Fe(II)EDTA absorption

A mixed absorbent had been proposed to enhance the chemical absorption–biological reduction process for NOx removal from flue gas. The mole ratio of the absorbent of Fe(II)Cit to Fe(II)EDTA was selected to be 3. After the biofilm was formed adequately, some influential factors, such as the concentration of NO, O2, SO2 and EBRT were investigated. During the long-term running, the system could keep on a steady NO removal efficiency (up to 90%) and had a flexibility in the sudden changes of operating conditions when the simulated flue gas contained 100–500ppm NO, 100–800ppm SO2, 1–5% (v/v) O2, and 15% (v/v) CO2. However, high NO concentration (>800ppm) and relative short EBRT (<100s) had significant negative effect on NO removal. The results indicate that the new system by using mixed-absorbent can reduce operating costs in comparison with the single Fe(II)EDTA system and possesses great potential for scale-up to industrial applications.

Spherules with pure iron cores from Myanmar jadeitite: Type-I deep-sea spherules?

Here we report spherules in Myanmar jadeitite, a rock forming from jadeitic fluids within mantle-derived serpentinized rocks in subduction zones under high-pressure conditions (>1.0 GPa) and rather low temperatures of about 250–370 °C. The spherules have off-centre iron nuclei and dendritic wüstite cortexes, with tiny wüstite crystals perpendicular to the surface of iron core. Within the spherules are vesicles occupied by calcite, jadeite, albite? or mixtures of these phases, and the cortexes contain about 10 wt.% SiO 2 + Al 2O 3 + Na 2O filling materials within wüstite. The spherules are in direct contact with jadeite crystals. Contrasting patterns of some individual spherules are obvious between a front area with a crowd of hill-like prominences and a rear zone with one or more rings on the surface. Such surface features and internal textures suggest that they experienced movement at high temperature and then rapid cooling. Chemical compositions of the nuclei are homogenous and consist of nearly pure iron with minor Cr (<0.05 wt.%), Mn (<0.80 wt.%), and Ni (0.142–0.23 wt.%), and a trend of Ni decreasing and Cr increasing from core to cortex. Mn in the cortex (up to about 2.00 wt.%) is far more enriched than the nucleus. The bulk ratios (average) of δ 56Fe and δ 57Fe in the core and cortex are 0.51and 0.78, respectively. Such features suggest that there is a very low possibility of origin associated with volcanic explosive eruption, impact ejecta, chemical reduction or oxidation of iron on seafloor. Since biological reduction processes are not significant under high P/T condition in subduction zones, this origin is excluded. Considering their low Ni contents, it is more likely that they belong to the minor type-I deep-sea cosmic spherules/dusts of low isotope fractionation. This discovery shows that such spherules could remain stable under low-temperature and high-pressure conditions during recycling processes, and therefore could be found in rocks related to slab-derived sediments within subduction zones. This also suggests that subducted oceanic slab sediments contribute to the formation of jadeitite, coupled with dehydration of sediments and altered oceanic crust.

New perspectives in aquatic redox chemistry: Abiotic transformations of pollutants in groundwater and sediments

Presented is a review of recent advances in the chemistry of abiotic redox transformations of organic pollutants in anaerobic ecosystems. The goal is to provide an indication of the state of knowledge and the remaining difficulties, rather than an exhaustive review of the existing literature. Particular attention is given to the types of functional groups that undergo reaction and the findings concerning physical and chemical parameters of ecosystems that govern the rates and products of redox transformations. Classes of compounds and structural features within these classes of compounds provide information about the intrinsic nature of the natural reductants. Further information is provided by studies which consider system variables such as sediment concentrations, organic carbon levels, pH, Eh and temperature. While the identity of reducing agents that transform organic pollutants in anaerobic systems remains elusive, the reactivities of these agents are being characterized and compared with surrogate (model) reductants. It is apparent that chemical and biological reduction processes are strongly coupled, and there is increasing evidence for widespread mediation of reductive reactions by bio-organic molecules.