Methyl Tert-butyl Ether Degradation Research Articles

A multicomponent propane monooxygenase catalyzes the initial degradation of methyl tert-butyl ether in Mycobacterium vaccae JOB5.

Methyl tert-butyl ether (MTBE) has been recognized as a groundwater contaminant due to its widespread distribution and potential threat to human health. The limited understanding of the enzymes catalyzing MTBE degradation restricts their application in MTBE bioremediation. In this study, an MTBE-degrading soluble di-iron monooxygenase that clusters phylogenetically with a known propane monooxygenase (PRM) encoded by the prmABCD gene cluster was identified and functionally characterized, revealing their role in MTBE metabolism by Mycobacterium vaccae JOB5. Transcriptome analysis demonstrated that the expression of prmABCD was upregulated when JOB5 was induced by MTBE. Escherichia coli Rosetta heterologously expressing prmABCD from JOB5 could transform MTBE, indicating that the PRM of JOB5 is capable of the initial degradation of MTBE. The loss of the gene encoding the oxygenase α-subunit or β-subunit, the coupling protein, or the reductase disrupted MTBE transformation by the recombinant E. coli Rosetta. In addition, the catalytic capacity of PRM is likely affected by residue G95 in the active site pocket and residues I84, P165, A269, and V270 in the substrate tunnel structure. Mutation of amino acids in the active site and substrate tunnel resulted in inefficiency or inactivation of MTBE degradation, and the activity in 1,4-dioxane (1,4-D) degradation was diminished less than that in MTBE degradation.IMPORTANCEMulticomponent monooxygenases catalyzing the initial hydroxylation of MTBE are important in MTBE biodegradation. Previous studies of MTBE degradation enzymes have focused on P450s, alkane monooxygenase and MTBE monooxygenase, but the vital role of soluble di-iron monooxygenases has rarely been reported. In this study, we deciphered the essential catalytic role of a PRM and revealed the key residues of the PRM in MTBE metabolism. Our findings provide new insight into the MTBE-degrading gene cluster and enzymes in bacteria. This characterization of the PRM associated with MTBE degradation expands our understanding of MTBE-degrading gene diversity and provides a novel candidate enzyme for the bioremediation of MTBE-contaminated sites.

Highly efficient degradation of MTBE by γ-Al2O3/NiO/TiO2 core- shell nanocomposite under visible light irradiation

γ-Al2O3/ NiO/ TiO2 as a novel photocatalyst that is active in visible light was synthesized by a simple sol-gel method. The prepared samples were characterized by XRD, DRS-UV/Vis, and TEM analysis. The photocatalytic effect of synthesized samples was examined on methyl tert-butyl ether (as a model hazardous contaminant) degradation. Experimental condition including pH, irradiation time, and photocatalyst mass were optimized. Overall, the UV/Vis spectrophotometry results indicated that the synthesized nanoparticles have an extraordinary photocatalytic activity for the degradation of methyl tert-butyl ether under visible light.

Photocatalytic Removal of Methyl Tert-Butyl Ether by C-N-TiO2 Nanoparticles from Aqueous Solution

BackgroundThe elimination of methyl tert-butyl ether (MTBE) from water resources remains a main environmental concern. In the present study, photo-assissted process for removal of MTBE was examined in the solutions containing C-N-TiO2 nanoparticles under UV irradiation in the batch mode.MethodsThe effects of operational factors such as pH, initial catalyst concentration, and initial MTBE concentration on MTBE removal was investigated.ResultsThe optimum degradation condition for MTBE was obtained at pH 7, catalyst load of 100 mg/L, air flow rate = 0.1 L/min and C0 = 5 mg/L with 73 percent degradation of MTBE at 60 min. In addition, Analytical profiles on MTBE removal were based on the first-order kinetics model. However, the removal rate decreased by increasing initial concentration of MTBE.ConclusionThe findings showed that UV/C-N-TiO2 system is an efficient method for MTBE degradation from aqueous solution.

Photocatalytic Oxidation of Methyl Tert-Butyl Ether in Presence of Various Phase Compositions of TiO2

MTBE (methyl tert-butyl ether) represents a rising threat to the environment, especially drinking water, and its effective removal (with all by-products) is necessary. Even a very low concentration of MTBE makes the water undrinkable; therefore, an effective treatment has to be developed. This work is focused on MTBE photocatalytic oxidation in presence of various TiO2 photocatalysts with different phase composition prepared by different methods. It was confirmed the phase composition of TiO2 had the most significant influence on the photocatalytic degradation of MTBE. The rutile phase more easily reduces adsorbed oxygen by photogenerated electrons to superoxide radical, supporting separation of charge carriers. The presence and concentrations of by-products have to be taken into account as well. The conversion of total organic carbon (TOC) was used for the comparison, 40% of TOC was removed after 1 h of irradiation in presence of TiO2–ISOP–C/800 photocatalyst composed of anatase and rutile phase.

Photocatalytic Degradation of Different VOCs in the Gas-Phase over TiO2 Thin Films Prepared by Ultrasonic Spray Pyrolysis

In this study, we deposited TiO2 thin films onto borosilicate glass by ultrasonic spray pyrolysis at 350 and 450 °C. The aim of study is to determine the effect of deposition temperature on photocatalytic activity of TiO2 thin films and to investigate the performance of TiO2 thin films on photocatalytic degradation of methyl tert-butyl ether (MTBE), acetone, acetaldehyde, and heptane as functions of different operating parameters. TiO2 thin films deposited at 350 and 450 °C have a thickness value of 190 and 330 nm, respectively. All as-prepared TiO2 films possess an anatase crystalline structure. According to the X-ray photon spectroscopy (XPS) study, the TiO2 thin film deposited at 350 °C showed a higher amount of oxygen vacancies and hydroxyl groups on the film surface after UV treatment. The aged-TiO2 thin film deposited at 350 °C showed a water contact angle (WCA) value of 0° after 10 min UV irradiation, showing superhydrophilic surface behavior. The TiO2 film deposited at 350 °C exhibited the highest amount of conversion of MTBE (100%). The results also showed that TiO2 films are capable of photocatalytic degradation of MTBE (100%) and acetaldehyde (approx. 80%) in humid air conditions and high airflow rate. The visible-light-activity of TiO2 thin films was tested with 5 ppm MTBE and acetone. TiO2 thin films deposited at 350 °C with a surface area of 600 cm2 showed 60% of MTBE and 33% of acetone degradation under VIS light.

VUV/Fe(II)/H2O2 as a novel integrated process for advanced oxidation of methyl tert-butyl ether (MTBE) in water at neutral pH: Process intensification and mechanistic aspects

Vacuum UV (VUV) technologies have recently attracted high interest due to their high efficacy in generating reactive oxygen species (ROS). To date, no systematic study of the modes of action of the integrated VUV/Fe(II)/H2O2 process against contaminants elimination exists; the present study reports the oxidation of MTBE in a new light-assisted Fenton-process, by employing either narrowband UVC (254 nm) or VUV (185 and 254 nm) irradiation, in a comparative evaluation. The processes under investigation were the UVC- or VUV/Fe(II)/H2O2 sensitized ones and their constituents, i.e. Fe(II)/H2O2, VUV, VUV/Fe(II), VUV/H2O2, VUV/Fe(II)/H2O2, as well as the UVC, UVC/H2O2 and UVC/Fe(II)/H2O2. We scrutinize the operational parameters of the VUV-assisted process, its enhancements and synergies, comparison with the UVC-based ones, as well as their inflicted pathways towards MTBE degradation. Complete degradation and 87.8% mineralization of 50 mg/L MTBE was achieved in the VUV/Fe(II)/H2O2 process (0.9 mM Fe(II) and 3 mM H2O2), at near-neutral pH (reaction times: ∼30 and 60 min, respectively). Irradiation with VUV light was found to act synergistically and in high kinetic rates enhancement compared to the UVC source, sensitizing the Fenton process for effective oxidation of MTBE in the aqueous solution. A scavenger study and degradation by-products investigation has been performed, leading to a mechanistic pathway proposition, elucidating MTBE degradation. The VUV/Fe(II)/H2O2 process demonstrated potential applicability in the field since it could efficiently treat (100% degradation and 86.4% mineralization) groundwater spiked with MTBE, operated either under batch or continuous-flow mode. The findings clearly indicates the VUV-assisted Fenton as an emerging and viable technology for field application to treat the MTBE-contaminated effluents or waters.

The in situ treatment of BTEX, MTBE, and TBA in saline groundwater

AbstractA pilot‐scale test was conducted in a saline aquifer to determine if a petroleum hydrocarbon (PHC) plume containing benzene (B), toluene (T), ethylbenzene (E), xylenes (X), methyl tert‐butyl ether (MTBE), and tert‐butyl alcohol (TBA) could be treated effectively using a sequential treatment approach that employed in situ chemical oxidation (ISCO) and enhanced bioremediation (EBR). Chemical oxidants, such as persulfate, have been shown to be effective in reducing dissolved concentrations of BTEX (B + T + E + X) and additives such as MTBE and TBA in a variety of geochemical environments including saline aquifers. However, the lifespan of the oxidants in saline environments tends to be short‐lived (i.e., hours to days) with their effectiveness being limited by poor delivery, inefficient consumption by nontargeted species, and back‐diffusion processes. Similarly, the addition of electron acceptors has also been shown to be effective at reducing BTEX and associated additives in saline groundwater through EBR, however EBR can be limited by various factors similar to ISCO. To minimize the limitations of both approaches, a pilot test was carried out in a saline unconfined PHC‐impacted aquifer to evaluate the performance of an engineered, combined remedy that employed both approaches in a sequence. The PHC plume had total BTEX, MTBE, and TBA concentrations of up to 4,584; 55,182; and 1,880 μg/L, respectively. The pilot test involved injecting 13,826 L of unactivated persulfate solution (19.4 weight percent (wt.%) sodium persulfate (Na2S2O8) solution into a series of injection wells installed within the PHC plume. Parameters monitored over a 700‐day period included BTEX, MTBE, TBA, sulfate, and sulfate isotope concentrations in the groundwater, and carbon and hydrogen isotopes in benzene and MTBE in the groundwater. The pilot test data indicated that the BTEX, MTBE, and TBA within the PHC plume were treated over time by both chemical oxidation and sulfate reduction. The injection of the unactivated persulfate resulted in short‐term decreases in the concentrations of the BTEX compounds, MTBE, and TBA. The mean total BTEX concentration from the three monitoring wells within the pilot‐test area decreased by up to 91%, whereas MTBE and TBA mean concentrations decreased by up to 39 and 58%, respectively, over the first 50 days postinjection in which detectable concentrations of persulfate remained in groundwater. Concentrations of the BTEX compounds, MTBE, and TBA rebounded at the Day 61 marker, which corresponded to no persulfate being detected in the groundwater. Subsequent monitoring of the groundwater revealed that the concentrations of BTEX continued to decrease with time suggesting that EBR was occurring within the plume. Between Days 51 and 487, BTEX concentrations decreased an additional 84% from the concentration measured on Day 61. Mean concentrations of MTBE showed a reduction during the EBR phase of remediation of 33% while the TBA concentration appeared to decrease initially but then increased as the sulfate concentration decreased as a result of MTBE degradation. Isotope analyses of dissolved sulfate (34S and 18O), and compound‐specific isotope analysis (CSIA) of benzene and MTBE (13C and 2H) supported the conclusions that ISCO and EBR processes were occurring at different stages and locations within the plume over time.

Use of omic tools to assess methyl tert-butyl ether (MTBE) degradation in groundwater.

This study employed innovative technologies to evaluate multiple lines of evidence for natural attenuation (NA) of methyl tertiary-butyl ether (MTBE) in groundwater at the 22 Area of Marine Corps Base (MCB) Camp Pendleton after decommissioning of a biobarrier system. For comparison, data from the 13 Area Gas Station where active treatment of MTBE is occurring was used to evaluate the effectiveness of omic techniques in assessing biodegradation. Overall, the 22 Area Gas Station appeared to be anoxic. MTBE was detected in large portion of the plume. In comparison, concentrations of MTBE at the 13 Area Gas Station were much higher (42,000 μg/L to 2800 μg/L); however, none of the oxygenates were detected. Metagenomic analysis of the indigenous groundwater microbial community revealed the presence of bacterial strains known to aerobically and anaerobically degrade MTBE at both sites. While proteomic analysis at the 22 Area Gas Station showed the presence of proteins of MTBE degrading microorganisms, the MTBE degradative proteins were only found at the 13 Area Gas Station. Taken together, these results provide evidence for previous NA of MTBE in the groundwater at 22 Area Gas Station and demonstrate the effectiveness of innovative-omic technologies to assist monitored NA assessments.

Modeling the efficiency of TiO2 photocatalytic degradation of MTBE in contaminated water: a support vector regression approach

Methyl tert-Butyl Ether (MTBE) is one of the common environmental contaminants that pose severe risks to human health and the environment. Due to the detrimental effects of MTBE, many efforts have been devoted towards decontamination of wastewater containing MTBE. Most of the reports on the treatment of MTBE are experimental based, which requires studying the effect of several factors such as dosage of the photocatalyst, pH of the medium, the initial concentration of contaminant and the contact time on degradation efficiency in MTBE contaminated waters. Although, this approach is highly dependable and often leads to new insights. However, because the degradation efficiency is influenced by multiple factors, performing experiments to investigate the effect of these factors often increases the experimental burden, thus requiring more time and materials consumption to achieve desirable results. Herein, we propose a computational intelligent strategy to mitigate these challenges. In this contribution, the degradation efficiencies of MTBE in the presence of TiO2/UV were modeled under various experimental conditions using the support vector regression model. The model was built using experimental data comprising of inputs such as TiO2 dose, initial MTBE concentration, UV wavelength and contact time. Remarkably, the developed model exhibits significant accuracy as determined from the values of correlation coefficient (98.27%) and root means square error (5.53). In addition, it was determined that the achievable optimum conditions for degradation of 0.5–100 ppm MTBE-contaminated water were 2.4 g/L of TiO2 dose with UV radiation, a solution pH of 3 and treatment time of 2 h. This study will be useful in the experimental design of treatment for MTBE, consequently reducing the time spent on running experiments and at the same time ensuring efficient use of resources for treatment of MTBE contaminated water.

TiO2 thin films by ultrasonic spray pyrolysis as photocatalytic material for air purification.

In this study, we showed that the TiO2 thin films deposited onto window glass are practicable for air purification and self-cleaning applications. TiO2 films were deposited onto window glass by ultrasonic spray pyrolysis method. Different deposition temperatures were used in the range of 250–450°C. The structural, morphological, optical properties and surface chemical composition were investigated to understand probable factors affecting photocatalytic performance and wettability of the TiO2 thin films. The TiO2 thin films were smooth, compacted and adhered adequately on the substrate with a thickness in the range of 100–240 nm. X-ray diffraction patterns revealed that all the TiO2 thin films consisted of anatase phase structure with the mean crystallite size in the range of 13–35 nm. The optical measurements showed that the deposited films were highly transparent (approx. 85%). The wettability test results showed that the TiO2 thin films sprayed at 350°C and 450°C and annealed at 500°C for 1 h were superhydrophilic. The photocatalytic activity of the films was tested for the degradation of methyl tert-butyl ether (MTBE) in multi-section plug-flow reactor. The TiO2 film deposited at 350°C exhibited the highest amount of conversion of MTBE, approximately 80%.

Characterization of co-metabolic biodegradation of methyl tert-butyl ether by a Acinetobacter sp. strain.

Co-metabolic bioremediation is a promising approach for the elimination of methyl tert-butyl ether (MTBE), which is a common pollutant found worldwide in ground water. In this paper, a bacterial strain able to co-metabolically degrade MTBE was isolated and named as Acinetobacter sp. SL3 based on 16S rRNA gene sequencing analysis. Strain SL3 could grow on n-alkanes (C5–C8) accompanied with the co-metabolic degradation of MTBE. The number of carbons present in the n-alkane substrate significantly influenced the degradation rate of MTBE and accumulation of tert-butyl alcohol (TBA), with n-octane resulting in a higher MTBE degradation rate (Vmax = 36.7 nmol min−1 mgprotein−1, Ks = 6.4 mmol L−1) and lower TBA accumulation rate. A degradation experiment in a fed-batch reactor revealed that the efficiency of MTBE degradation by Acinetobacter sp. strain SL3 did not show an obvious decrease after nine rounds of MTBE replenishment ranging from 0.1–0.5 mmol L−1. The results of this paper reveal the preferable properties of Acinetobacter sp. SL3 for the bioremediation of MTBE via co-metabolism and leads towards the development of new MTBE elimination technologies.

Stabilized hydrogen peroxide for the remediation of hydrocarbons and MTBE in high temperature and saline groundwater

AbstractA field pilot‐scale test was conducted to determine if the use of citric acid‐stabilized hydrogen peroxide (H2O2) is effective in reducing dissolved concentrations of petroleum hydrocarbon compounds (PHCs) and the additive methyl tert‐butyl ether (MTBE) in impacted high salinity groundwater. The test was carried out adjacent to an operational hydrocarbon fuel facility in Western Saudi Arabia. The pilot test was based on the results of laboratory tests, which suggested that hydrogen peroxide stabilized with citric acid (C6H8O7) would enhance the degradation of the dissolved PHCs and associated MTBE within a saline groundwater. A 7.5 weight percent hydrogen peroxide solution was injected into a series of injection wells positioned to target a PHC‐impacted plume within an unconfined aquifer. The plume contains total benzene, toluene, ethylbenzene, and xylenes (BTEX) at concentrations up to 6,890 micrograms per liter (μg/L). The MTBE concentration within the groundwater was detected at concentrations of up to 55,182 μg/L, whereas the groundwater salinity was approximately 7,000 milligrams per liter (mg/L). A total of 9,012 liters of citric acid‐stabilized hydrogen peroxide solution was injected over three events spaced over a 1‐month period. The results of the pilot test indicated that injection of stabilized hydrogen peroxide was effective in reducing the concentration of dissolved PHCs within the plume, including BTEX and other aromatic hydrocarbons. The average concentration decrease for total BTEX was 72% with up to 97.4% reduction being measured in a sample collected from one key monitoring well during the treatment period. MTBE was also effectively treated during the pilot test with an average MTBE degradation of 50% being realized during the test and up to 86% concentration decrease being measured in some groundwater samples. While reductions in MTBE concentrations were noted, no increase in tertiary butyl alcohol was measured, which is a promising finding. The general water quality did not fluctuate significantly between pre‐ and postinjection with the pH, oxidation–reduction potential, and dissolved oxygen remaining relatively constant. The dissolved iron, nitrate, and sulfate concentrations vary during the injection period with nitrate decreasing to below detection limits following the final injection, whereas sulfate decreased in two of the three monitoring wells following the injection. Dissolved iron concentrations remained relatively constant in two of the three monitoring wells (NJBP45 and NJBP46) during the injection events, whereas dissolved iron in monitoring well NJBP44 decreased from a baseline concentration of 1.03 μg/L to 0.09 μg/L, suggesting that the ferrous iron in solution was being oxidized to ferric iron. Measurements of the preinjection microbiological community indicated that the community is diverse within the injection area based on deoxyribonucleic acid extraction by polymerase chain reaction as well as sequencing and clustering. Subsequent analyses of the microbiological community postinjection indicated that the community diversity and biomass was reduced with a shift to a more aerobic population, at least over the short term. Results of compound specific isotope analyses are consistent with the concentration data and show petroleum hydrocarbon and MTBE was degraded by the citric acid‐stabilized hydrogen peroxide treatment.

One‐step synthesis of NiO nano‐photocatalyst by wire explosion process and its application in photocatalytic degradation of Methyl tert‐butyl ether

AbstractThe use of the gasoline additive methyltert‐butyl ether (MTBE) has caused serious concern about groundwater and surface water contamination. In this study, UV light/ NiO nano‐photocatalyst (NiONP) system was firstly used to degradation of MTBE in contaminated water. A low‐cost and environmentally clean exploded‐wire plasma technique based on cheap solid nickel source is developed for preparation of NiONP. Optical, magnetic and physicochemical properties were successfully characterized using DRS, VSM, XRD, SEM, EDX, TEM and BET techniques. The NiONP exhibits excellent photocatalytic degradation ability of MTBE. The degradation process was monitored during the photocatalytic reaction by gas chromatography‐mass spectrometry (GC‐MS). It has been found that MTBE undergoes a series of intermediate step, which leads to form a number of intermediate products, mainly acetone, formic acid and t‐butyl formate (TBF). According to the results of the intermediates determination, a possible pathway degradation of MTBE was also proposed.

ELIMINACIÓN MEJORADA DE METIL TERC-BUTIL ÉTER POR UN CONSORCIO BACTERIANO SUPLEMENTADO CON EXTRACTO DE LEVADURA

Methyl tert-butyl ether (MTBE) is highly soluble in water and considered a contaminant. Although MTBE can be removed by microbial consortia its removal efficiency is low due to its toxic effect on microbial growth. An alternative to enhance the MTBE degradation efficiency is by cometabolism. Yeast extract (cometabolite) was studied in the EB-MTBE-24 consortium to enhance the MTBE degradation efficiency in cultures at 110 mg L-1 of MTBE and in cultures at 110 mg L-1 of MTBE supplemented with 100 and 500 mg L-1 of yeast extract (100YE and 500YE, respectively). The 100YE culture presented higher values of​ mmax= 0.07±0.02 h-1, degradation efficiency 77.63 ± 1.16 % and a global degradation rate 0.90 ± 0.05 h-1 than the culture without YE addition. The 500YE culture presented the lowest MTBE degradation efficiency. The kinetics of MTBE degradation for the 100YE culture is described by first-order and pseudo-first-order reaction models. The cultivable fraction of the EB-MTBE-24 consortium is constituted by Sphingobium barthaii C1, Gordonia polyisoprenivorans C2, and Ochrobactrum anthropi C3. The 100YE culture of the EB-MTBE-24 consortium possess a greater potential to degrade high MTBE concentrations at a high rate suggesting that the YE minimizes the MTBE inhibitory effect on microbial growth.

Anaerobic degradation of a mixture of MtBE, EtBE, TBA, and benzene under different redox conditions

The increasing use of biobased fuels and fuel additives can potentially change the typical fuel-related contamination in soil and groundwater. Anaerobic biotransformation of the biofuel additive ethyl tert-butyl ether (EtBE), as well as of methyl tert-butyl ether (MtBE), benzene, and tert-butyl alcohol (TBA, a possible oxygenate metabolite), was studied at an industrially contaminated site and in the laboratory. Analysis of groundwater samples indicated that in the field MtBE was degraded, yielding TBA as major product. In batch microcosms, MtBE was degraded under different conditions: unamended control, with medium without added electron acceptors, or with ferrihydrite or sulfate (with or without medium) as electron acceptor, respectively. Degradation of EtBE was not observed under any of these conditions tested. TBA was partially depleted in parallel with MtBE. Results of microcosm experiments with MtBE substrate analogues, i.e., syringate, vanillate, or ferulate, were in line with the hypothesis that the observed TBA degradation is a cometabolic process. Microcosms with ferulate, syringate, isopropanol, or diethyl ether showed EtBE depletion up to 86.5% of the initial concentration after 83 days. Benzene was degraded in the unamended controls, with medium without added electron acceptors and with ferrihydrite, sulfate, or chlorate as electron acceptor, respectively. In the presence of nitrate, benzene was only degraded after addition of an anaerobic benzene-degrading community. Nitrate and chlorate hindered MtBE, EtBE, and TBA degradation.

Photocatalytic Degradation of Methyl Tert-Butyl Ether (MTBE) from Aqueous Solution: A Review

Photocatalytic Degradation of Methyl Tert-Butyl Ether (MTBE) from Aqueous Solution: A Review

BSocial: Deciphering Social Behaviors within Mixed Microbial Populations.

Ecosystem functionality depends on interactions among populations, of the same or different taxa, and these are not just the sum of pairwise interactions. Thus, know-how of the social interactions occurring in mixed-populations are of high interest, however they are commonly unknown due to the limitations posed in tagging each population. The limitations include costs/time in tediously fluorescent tagging, and the number of different fluorescent tags. Tag-free strategies exist, such as high-throughput sequencing, but ultimately both strategies require the use of expensive machinery. Our work appoints social behaviors on individual strains in mixed-populations, offering a web-tool (BSocial http://m4m.ugr.es/BSocial.html) for analyzing the community framework. Our quick and cheap approach includes the periodic monitoring of optical density (OD) from a full combinatorial testing of individual strains, where number of generations and growth rate are determined. The BSocial analyses then enable us to determine how the addition/absence of a particular species affects the net productivity of a microbial community and use this to select productive combinations, i.e., designate their social effect on a general community. Positive, neutral, or negative assignations are applied to describe the social behavior within the community by comparing fitness effects of the community against the individual strain. The usefulness of this tool for selection of optimal inoculum in biofilm-based methyl tert-butyl ether (MTBE) bioremediation was demonstrated. The studied model uses seven bacterial strains with diverse MTBE degradation/growth capacities. Full combinatorial testing of seven individual strains (triplicate tests of 127 combinations) were implemented, along with MTBE degradation as the desired function. Sole observation of highest species fitness did not render the best functional outcome, and only when strains with positive and neutral social assignations were mixed (Rhodococcus ruber EE6, Agrobacterium sp. MS2 and Paenibacillus etheri SH7), was this obtained. Furthermore, the use of positive and neutral strains in all its combinations had a significant higher degradation mean (x1.75) than exclusive negative strain combinations. Thus, social microbial processes benefit bioremediation more than negative social microbial combinations. The BSocial webtool is a great contributor to the study of social interactions in bioremediation processes, and may be used in other natural or synthetic habitat studies.

Heterogeneous persulfate oxidation of BTEX and MTBE using Fe3O4−CB magnetite composites and the cytotoxicity of degradation products

Groundwater contamination by organic aromatic compounds such as gasoline fuel is a serious worldwide problem because of their carcinogenic and mutagenic potential. This study evaluated the use of Fe3O4−carbon black (CB) composites for persulfate (PS) oxidation of benzene, toluene, ethylene, and xylene (BTEX) and methyl tert-butyl ether (MTBE) compounds from the aqueous solution. The characterization results of environmental scanning electron microscopy coupled with energy-dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and a superconducting quantum interference device magnetometry evidenced the successful synthesis of Fe3O4−CB composites. In addition, the in vitro cytotoxic activity and apoptotic response of these composites were investigated before and after the Fe3O4−CB/PS processes test of the BTEX and MTBE samples was performed. The effects of various operating parameters were evaluated to optimize the oxidation process, including the PS concentration, initial pH, and Fe3O4−CB amount. The results showed that increasing PS and Fe3O4−CB dosage could accelerate BTEX and MTBE oxidation when PS and Fe3O4−CB concentrations increased to 15 g L−1 and 1.0 g L−1, respectively, at a pH of 3.0. The degradation rate of BTEX and MTBE was strongly pH-dependent. Methyl thiazolyl tetrazolium assay was employed to perform a cytotoxicity study after Fe3O4−CB/PS processing treatment of BTEX and MTBE degradation products on the zebrafish (Danio rerio) embryonic cell line (ZF4), which revealed that a weak effect and apoptosis in cell viability ultimately leads to cell death. The results suggested that Fe3O4−CB assisted persulfate oxidation without elevating the temperature is a suitable and economic alternative for the ex-situ treatment of BTEX- and MTBE-contaminated aquatic environments.

Polypyrrole-Grafted Coconut Shell Biological Carbon as a Potential Adsorbent for Methyl Tert-Butyl Ether Removal: Characterization and Adsorption Capability.

Methyl tert-butyl ether (MTBE) has been used as a common gasoline additive worldwide since the late twentieth century, and it has become the most frequently detected groundwater pollutant in many countries. This study aimed to synthesize a novel microbial carrier to improve its adsorptive capacity for MTBE and biofilm formation, compared to the traditional granular activated carbon (GAC). A polypyrrole (PPy)-modified GAC composite (PPy/GAC) was synthesized, and characterized by Fourier transform infrared spectroscopy (FT-IR) and Brunauer-Emmett-Teller (BET) surface area analysis. The adsorption behaviors of MTBE were well described by the pseudo-second-order and Langmuir isotherm models. Furthermore, three biofilm reactors were established with PPy/GAC, PPy, and GAC as the carriers, respectively, and the degradation of MTBE under continuous flow was investigated. Compared to the biofilm reactors with PPy or GAC (which both broke after a period of operation), the PPy/GAC biofilm column produced stable effluents under variable treatment conditions with a long-term effluent MTBE concentration <20 μg/L. Pseudomonas aeruginosa and Acinetobacter pittii may be the predominant bacteria responsible for MTBE degradation in these biofilm reactors.

Biodegradation of Methyl tert-Butyl Ether by Co-Metabolism with a Pseudomonas sp. Strain.

Co-metabolic bioremediation is supposed to be an impressive and promising approach in the elimination technology of methyl tert-butyl ether (MTBE), which was found to be a common pollutant worldwide in the ground or underground water in recent years. In this paper, bacterial strain DZ13 (which can co-metabolically degrade MTBE) was isolated and named as Pseudomonas sp. DZ13 based on the result of 16S rRNA gene sequencing analysis. Strain DZ13 could grow on n-alkanes (C5-C8), accompanied with the co-metabolic degradation of MTBE. Diverse n-alkanes with different carbon number showed a significant influence on the degradation rate of MTBE and accumulation of tert-butyl alcohol (TBA). When Pseudomonas sp. DZ13 co-metabolically degraded MTBE with n-pentane as the growth substrate, a higher MTBE-degrading rate (Vmax = 38.1 nmol/min/mgprotein, Ks = 6.8 mmol/L) and lower TBA-accumulation was observed. In the continuous degradation experiment, the removal efficiency of MTBE by Pseudomonas sp. Strain DZ13 did not show an obvious decrease after five times of continuous addition.