Methyl Tert-butyl Ether Degradation Rate Research Articles

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.

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.

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.

Stenotrophomonas maltophilia isolated from gasoline-contaminated soil is capable of degrading methyl tert-butyl ether

Background: Methyl tert-butyl ether (MTBE) is a pollutant that causes deleterious effects on human and environmental health. Certain microbial cultures have shown the ability to degrade MTBE, suggesting that a novel bacterial species capable of degrading MTBE could be recovered. The goal of this study was to isolate, identify and characterize the members of a bacterial consortium capable of degrading MTBE. Results: The IPN-120526 bacterial consortium was obtained through batch enrichment using MTBE as the sole carbon and energy source. The cultivable fraction of the consortium was identified; of the isolates, only Stenotrophomonas maltophilia IPN-TD and Sphingopyxis sp. IPN-TE were capable of degrading MTBE. To the best of our knowledge, this report is the first demonstrating that S. maltophilia and Sphingopyxis sp. are capable of degrading MTBE. The degradation kinetics of MTBE demonstrated that S. maltophilia IPN-TD had a significantly higher overall MTBE degradation efficiency and rate (48.39 ± 3.18% and 1.56 ± 0.12 mg L -1 h -1 , respectively) than the IPN-120526 consortium (38.59 ± 2.17% and 1.25 ± 0.087 mg L -1 h -1 , respectively). The kinetics of MTBE removal by both cultures fit first-order and pseudo-first-order reaction models. Conclusions: These findings suggest that S. maltophilia IPN-TD in axenic culture has considerable potential for the detoxification of MTBE-contaminated water. Normal 0 21 false false false ES-TRAD JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabla normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Cambria,serif; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-ansi-language:ES-TRAD;}

Enhanced cometabolic degradation of methyl tert-butyl ether by a Pseudomonas sp. strain grown on n-pentane

When methyl tert-butyl ether (MTBE) is added as oxygenates it increases the octane number and decreases the release of nitric oxide from the incomplete combustion of reformulated gasoline. The extensive use of MTBE allowed it to be detectable as a pollutant in both ground-level and underground water worldwide. The present study focuses on the isolation and characterization of MTB-degrading microorganisms by cometabolism based on the results of growth on different carbon sources. It also focuses on the kinetic analysis and the continuous degradation of MTBE. A bacterial strain WL1 that can grow on both n-alkanes (C5-C8) and aromatics was isolated and named Pseudomonas sp. WL1 according to the 16S rDNA sequencing analysis. Strain WL1 could cometabolically degrade MTBE in the presence of n-alkanes with a desirable degradation rate. Diverse n-alkanes with different lengths of carbon chains showed significant influence on the degradation rate of MTBE and accumulation of tert-butyl alcohol (TBA). When strain WL1 cometabolically degraded MTBE in the presence of n-pentane, higher MTBE-degrading rate and lower TBA-accumulation were observed (Vmax = 38.1 nmol/min/mgprotei, Ks = 6.8 mmol/L). In the continuous degrading experiment, the removal efficiency of MTBE by Pseudomonas sp. WL1 did not show any obvious decrease after five subsequent additions.

Rapid biodegradation of methyl tert-butyl ether (MTBE) by pure bacterial cultures

Two pure bacterial strains capable of rapid degrading methyl tert-butyl ether (MTBE) were isolated from an industrial wastewater treatment plant, identified and characterized. These strains are able to grow on MTBE as the sole carbon and energy sources and completely mineralize it to the biomass and carbon dioxide. The strains were identified as Bacillus cereus and Klebsiella terrigena. Both strains are able to grow in the presence of 48 gl -1 MTBE in water, which is almost the maximum concentration of MTBE in the water. They were able to completely degrade 10 gl -1 MTBE in less than a day. The specific degradation rate of MTBE at optimum conditions were 5.89 and 5.78 g(MTBE) g(cells) -1 h -1 for B. cereus and K. terrigena, respectively. The biomass yield was 0.085 and 0.076 gg -1 , respectively. The cultivations were carried out successfully at 25, 30 and 37 °C, while they showed the best performance at 37 °C. Neither of the strains was able to grow and degrade MTBE anaerobically.

Aerobic degradation of methyl tert-butyl ether in a closed symbiotic system containing a mixed culture of Chlorella ellipsoidea and Methylibium petroleiphilum PM1

The contamination of groundwater by methyl tert-butyl ether (MTBE) is one of the most serious environmental problems around the world. MTBE degradation in a closed algal–bacterial symbiotic system, containing a mixed culture of Methylibium petroleiphilum PM1 and Chlorella ellipsoidea, was investigated. The algal–bacterial symbiotic system showed increased MTBE degradation. The MTBE-degradation rate in the mixed culture (8.808 ± 0.007 mg l −1 d −1) was higher than that in the pure bacterial culture (5.664 ± 0.017 mg l −1 d −1). The level of dissolved oxygen was also higher in the mixed culture than that in the pure bacterial culture. However, the improved efficiency of MTBE degradation was not in proportional to the biomass of the alga. The optimal ratio of initial cell population of bacteria to algae was 100:1. An immobilized culture of mixed bacteria and algae also showed higher MTBE degradation rate than the immobilized pure bacterial culture. A mixed culture with algae and PM1 immobilized separately in different gel beads showed higher degradation rate (8.496 ± 0.636 mg l −1 d −1) than that obtained with algae and PM1 immobilized in the same gel beads (5.424 ± 0.010 mg l −1 d −1).

Enhanced bioremediation of methyl tert-butyl ether (MTBE) by microbial consortia obtained from contaminated aquifer material

A microcosm study was carried out to evaluate the potential for biodegradation of methyl tert-butyl ether (MTBE) impacting groundwater at a former oil refinery site located in Naples (SW Italy). A screening of aerobic, anaerobic and co-metabolic aerobic conditions was carried out by triplicate batch reactors, using contaminated soil and groundwater from the study site. All microcosms were amended with ammonium and phosphate salts and, if aerobic, they were supplied with excess oxygen throughout the static incubation period of 6 months. Propane, pentane and n-hexane were selected as the primary substrates for co-metabolic treatments. After the initial lag phase (40–60 d), quantitative MTBE decay was repeatedly observed in the aerobic set amended only with nitrogen and phosphorus and further fed with MTBE, thus suggesting that the indigenous soil bacteria have the ability to degrade MTBE. All other treatments, i.e., anaerobic and co-metabolic aerobic, resulted unsuccessful after incubation extending up to 190 d. Bacterial consortia in the active microcosms were later enriched and further studied through second and third generation batch reactors with no soil, operated under continuous mixing for 5–7 months. MTBE degradation rate progressively increased with reactor operating time, following a zero order kinetics in the concentration range 1–10 mg L −1 and leading to a residual concentration of less than 10 μg L −1. The calculated maximum biodegradation rate was 20 mg MTBE g VSS −1 h −1. An accumulation of nitrite ions also occurred after long operating times, thus inhibiting MTBE degradation. This effect was minimized by replacing ammonium with nitrate. Identified degradation intermediates were tert-butyl alcohol and tert-butyl formate. Fluorescent in situ hybridization was applied for a preliminary microbiological screening of the consortia, suggesting that the detected cocci (about 0.5 and 1.5 μm diameter, respectively) and long bacilli with a narrow diameter might be as yet undescribed species.

Effects of co-substrates and inhibitors on the anaerobic O-demethylation of methyl tert-butyl ether (MTBE)

Methyl tert-butyl ether (MTBE) contamination is widespread in aquifers near urban areas around the world. Since this synthetic fuel oxygenate is resistant to most physical methods of treating fuel-contaminated water, biodegradation may be a useful means of remediation. Currently, information on anaerobic MTBE degradation is scarce. Depletion has been observed in soil and sediment microcosms from a variety of locations and under several redox conditions, but the responsible organisms are unknown. We are studying anaerobic consortia, enriched from contaminated sediments for MTBE-utilizing microorganisms for over a decade. MTBE degradation occurred in the presence of other fuel components and was not affected by toluene, benzene, ethanol, methanol, or gasoline. Many aryl O-methyl ethers, such as syringic acid, that are O-demethylated by acetogenic bacteria, were also O-demethylated by the MTBE-utilizing enrichment cultures. The addition of these compounds as co-substrates increased the rate of MTBE degradation, offering a potentially useful method of stimulating the MTBE degradation rate in situ. Propyl iodide caused light-reversible inhibition of MTBE degradation, suggesting that the MTBE degradation process is corrinoid dependent. The anaerobic MTBE degradation process was not directly coupled to methanogenesis or sulfidogenesis and was inhibited by the bactericidal antibiotic, rifampicin. These results suggest that MTBE degradation is mediated by acetogenic bacteria.

Biodegradation of methyl t-butyl ether by aerobic granules under a cosubstrate condition

Aerobic granules efficient at degrading methyl tert-butyl ether (MTBE) with ethanol as a cosubstrate were successfully developed in a well-mixed sequencing batch reactor (SBR). Aerobic granules were first observed about 100 days after reactor startup. Treatment efficiency of MTBE in the reactor during stable operation exceeded 99.9%, and effluent MTBE was in the range of 15-50 microg/L. The specific MTBE degradation rate was observed to increase with increasing MTBE initial concentration from 25 to 500 mg/L, which peaked at 22.7 mg MTBE/g (volatile suspended solids).h and declined with further increases in MTBE concentration as substrate inhibition effects became significant. Microbial-community deoxyribonucleic acid profiling was carried out using denaturing gradient gel electrophoresis of polymerase chain reaction-amplified 16S ribosomal ribonucleic acid. The reactor was found to be inhabited by several diverse bacterial species, most notably microorganisms related to the genera Sphingomonas, Methylobacterium, and Hyphomicrobium vulgare. These organisms were previously reported to be associated with MTBE biodegradation. A majority of the bands in the reactor represented a group of organisms belonging to the Flavobacteria-Proteobacteria-Actinobacteridae class of bacteria. This study demonstrates that MTBE can be effectively degraded by aerobic granules under a cosubstrate condition and gives insight into the microorganisms potentially involved in the process.

Biodegradation of methyl tert-butyl ether as a sole carbon source by aerobic granules cultivated in a sequencing batch reactor

Aerobic granules efficient at degrading methyl tert-butyl ether (MTBE) were successfully developed in a well-mixed sequencing batch reactor (SBR). Treatment efficiency of MTBE in the reactor during the stable operations exceeded 99.8%, and effluent MTBE was consistently below 800 microg/L. The specific MTBE degradation rate was observed to increase with increasing MTBE initial concentrations from 25 to 400 mg/L, peaked at 18.2 mg-MTBE/g-VSS h, and declined with further increases in MTBE concentration as substrate inhibition effects became significant. There was a good fit between these biodegradation data and the Haldane equation (R (2) = 0.976). Microbial community DNA profiling was carried out using denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction amplified 16S rDNA. The aerobic granule was found to contain a wide diversity of microorganisms. More than 70% similarity among the samples in the time period examined indicated a highly stable microbial community as the reactor reached the stable operation.

Influences of metals on kinetics of methyl tert-butyl ether biodegradation by Ochrobactrum cytisi

The influence of zinc, manganese, and nickel on the degradation of MTBE (methyl tert-butyl ether), by an aerobic MTBE-degrading strain, Ochrobactrum cytisi, were investigated. The result showed that unlike previous findings, O. cytisi was able to degrade MTBE through direct metabolism when MTBE was present as the only carbon source. The degradation rate of MTBE was rapid, completed within 80 h. MTBE biodegradation by this strain was stimulated at low concentrations of Zn 2+ (1–5 mg l −1) and Mn 2+ (1–5 mg l −1) but inhibited at high concentrations of Zn 2+ (20 mg l −1) and Mn 2+ (20 mg l −1), and at low concentration of Ni 2+ (1–4 mg l −1). Kinetic parameters for MTBE degradation in the presence or absence of metals were obtained through nonlinear regression and a least-square minimization procedure. In all cases, a good agreement was achieved between kinetic simulations and experimental results.

Effects of environmental settings on MTBE removal for a mixed culture and its monoculture isolation

A mixed culture was utilized to evaluate methyl tert-butyl ether (MTBE) removal under various conditions and to isolate a MTBE-degrading pure culture. The results showed that high MTBE removal efficiencies can be reached even in the presence of other substrates. The biodegradation sequence of the target compounds by the mixed culture, in order of removal rate, was toluene, ethyl benzene, p-xylene, benzene, MTBE, ethyl ether, tert-amyl methyl ether, and ethyl tert-butyl ether. In addition, preincubation of the mixed cultures with benzene and toluene showed no negative effect on MTBE removal; on the contrary, it could even increase the degradation rate of MTBE. The kinetic behavior showed that the maximum specific growth rate and the saturation constant of the mixed culture degrading MTBE are 0.000778 h(-1) and 0.029 mg l(-1), respectively. However, a high MTBE concentration (60 mg l(-1)) was slightly inhibiting to the growth of the mixed culture. The pure culture isolated from the enrichments in the bubble-air bioreactor showed better efficiency in MTBE removal than the mixed culture; whereas, tert-butyl alcohol was formed as a metabolic intermediate during the breakdown of MTBE.

Cometabolic Degradation of MTBE Using Methane‐Propane‐ and Butane‐Utilizing Enrichment Cultures and Rhodococcus sp. BU3

AbstractThe fuel oxygenated methyl tert‐butyl ether (MTBE) is used worldwide to replace leaded organic compounds. Although MTBE is persistent in the environment, chiefly due to its low biodegradability, some microbial cultures are able to mineralize it. This paper reports on the cometabolic degradation of MTBE by methane‐, propane‐ and butane‐utilizing enrichment cultures and the pure Rhodococcus sp. BU3 culture isolated from natural habitats. Three methane‐, three propane‐ and four butane‐utilizing cultures, which degrade MTBE cometabolically, were enriched. In experiments with resting cells at 20 °C, enrichment cultures grown on methane degraded MTBE at a maximum rate of 1.0 mg MTBE/(g biomass · h). Propane‐ and butane‐utilizing enrichment cultures degraded MTBE and the intermediate tert‐butyl alcohol (TBA) cometabolically at temperatures of 20 °C at maximum rates of 7.2 mg MTBE/(g biomass · h) and 5.2 mg MTBE/(g biomass · h), respectively. Propane‐utilizing cultures were also able to degrade MTBE and TBA consecutively after growth on 1‐propanol. However, the MTBE degradation rate after growth on 1‐propanol was lower than on propane. The isolated pure culture BU3 specified as Rhodococcus sp. degraded MTBE at maximum rates of 5.4 mg MTBE/(g biomass · h) when grown on propane and 2.3 mg MTBE/(g biomass · h) when grown on 1‐propanol, respectively. In column systems with recirculation, it is shown that Rhodococcus sp. BU3 degraded 95 mg/L MTBE over a time period of 6 days. The degradation activity of the immobilized bacteria could be regenerated by the addition of growth substrates (propanol or propane). The results of these experiments provide a promising basis for their implementation in an enhanced natural attenuation approach.

Effect of metals on biodegradation kinetics for methyl tert-butyl ether

Many ground waters are polluted with a complex mixture of organic and metal contaminants. Especially, the presence of heavy metals may be of particular concern, since they may be toxic for microorganisms and may interfere with the biodegradation process. A study of methyl tert-butyl ether (MTBE) biodegradation in the presence of heavy metals with the purpose of determining the effects of type and concentration of metals on reaction kinetics was undertaken. The experiments were performed as batch biodegradation experiments, and the kinetic parameters were determined by a nonlinear regression technique. Experimental results showed that the presence of Mn 2+ offers a slight stimulating effect on MTBE degradation; however, Cr 3+ and Zn 2+ resulted in less biodegradation at metal concentrations of 1 mg l −1. The inhibitory effect of adding metals was obvious, with constantly decreasing value of MTBE degradation rate in the following order Cu 2+ > Cr 3+ > Zn 2+ > Mn 2+ at metal concentrations 10 mg l −1 and 50 mg l −1. The kinetic parameters of μ m were found to be virtually unaffected until a threshold concentration (10 mg l −1) of metal was reached. However, a significant inhibitory effect on bacterial growth, as manifested by a decrease in both K i values for Cu 2+ (at 1 and 10 mg l −1), and both Cr 3+ and Zn 2+ (at 10 mg l −1).

Effect of Hydrogen Peroxide on the Photocatalytic Degradation of Methyl tert-butyl Ether

The photocatalytic degradation of methyl tert-butyl ether (MTBE) was investigated in the aqueous slurry of titanium dioxide (TiO2) particles irradiated with xenon lamp in a batch reactor, in the presence and absence of hydrogen peroxide. The reaction was found to follow a pseudo-first-order kinetics and the initial reaction rate constant increased by raising the TiO2 loading and reached an apparent optimum value at 0.5 g TiO2/L. The addition of small amounts of hydrogen peroxide to the TiO2 slurry, which is generally known to enhance the oxidation process in treating organic pollutants, decreased the initial MTBE degradation rate by as much as nearly 50%. However, this trend was reversed and reaction rate approached a plateau at higher concentration levels of hydrogen peroxide.

Advanced oxidation of methyl tert-butyl ether (MTBE) by UV/TiO2 and H2O2-UV/TiO2 processes

This study investigated photocatalysis of MTBE via both UV/TiO2 and H2O2-UV/TiO2 processes. Several experimental parameters including pH level, H2O2 concentration, TiO2 dosage and light intensity were investigated. The experimental results demonstrated the degradation of MTBE following a pseudo first-order reaction in both reaction systems. Faster degradation rates were observed in alkaline solution for the UV/TiO2 system, but for the H2O2-UV/TiO2 system, faster degradation rates were detected in acidic solution. More dosage of TiO2 and irradiated light intensity were beneficial for the photocatalysis of MTBE. However, a peak reaction rate was observed at a TiO2 concentration of about 500 mg/L. The experimental results also indicated that the degradation rate of MTBE was enhanced by the addition of H2O2. H2O2 could be a more efficient electron acceptor than oxygen for retarding recombination of electron–hole pairs. The degradation rate in the H2O2-UV/TiO2 system was about 2.8 times faster than that in the UV/TiO2 system for solution pH below 5, and the rate increased 30% for solution pH above 6. In addition, it is observed that the reaction rate of MTBE increased quickly with H2O2 concentration at low H2O2 dosages, but the rate was independent of H2O2 dosage when adding too much H2O2.

Methyl tert-butyl ether (MTBE) in snow samples in Germany

In the present study, experimental results of methyl tert-butyl ether (MTBE) analysis in 43 snow samples from 13 various locations during two winter seasons are presented. MTBE could be detected in 65% of the samples. The concentrations ranged from 11 to 631 ng L −1. The comparison to formerly analysed rainwater samples indicates atmospheric transfer of MTBE from urban to rural areas preferentially in winter due to lower atmospheric degradation rates and suggests that MTBE is more effectively scavenged from the atmosphere by snow than by rain. This result is in contrast to calculated distribution coefficients K Rain/Air (−6.8°) and K Snow/Air (−6.8°) using different values for the specific snow surface area. MTBE concentrations measured in the collected snow samples from rural areas did not differ from MTBE concentrations in snow samples collected in the urban area of Frankfurt/M. The explanatory factor for this finding is also the lower atmospheric degradation rate of MTBE in winter. Particular meteorological conditions at the monitoring site Schmücke most probably explain maximum concentrations of 631 and 438 ng L −1 measured at this site. Decreasing MTBE amounts in snow samples collected at the monitoring site Schauinsland in January 2003 might have been due to increasing ambient temperatures. Varying MTBE amounts in snow samples collected at the Taunus Observatorium (Kleiner Feldberg) in February 2002 and in January/February 2003 cannot be explained by ambient temperatures. In future studies concurrent air sampling and morphological characterisation of the sampled snow would be required to clarify and confirm the results of the present study.

Methyl tert-butyl Ether and tert-butyl Alcohol Degradation by Fusarium solani

Fusarium solani degraded methyl tert-butyl ether (MTBE) and other oxygenated compounds from gasoline including tert-butyl alcohol (TBA). The maximum degradation rate of MTBE was 16 mg protein h and 46 mg/g protein h for TBA. The culture transformed 77% of the total carbon to 14CO2. The estimated yield for MTBE was 0.18 g dry wt/g MTBE.

Anaerobic Biodegradation of Methyl tert‐Butyl Ether Under Iron‐Reducing Conditions in Batch and Continuous‐Flow Cultures

The feasibility of biodegradation of the fuel oxygenate methyl tert-butyl ether (MTBE) under iron-reducing conditions was explored in batch and continuous-flow systems. A porous pot completely-mixed reactor was seeded with diverse cultures and operated under iron-reducing conditions. For batch studies, culture from the reactor was transferred anaerobically to serum bottles containing either MTBE alone or MTBE with ethanol (EtOH) and excess electron acceptor. In the continuous-flow reactor, MTBE conversion to tert-butyl alcohol (TBA) was observed after 181 days of operation, and stable removal was achieved throughout the remainder of the study. Simultaneously, both the MTBE only and the MTBE and EtOH iron-reducing batch serum bottles also began to degrade MTBE. Bottles were respiked and the degradation rate was determined to be 2.36 +/- 0.10 x 10(-4) mmol MTBE/min-kgVSS. The EtOH present with MTBE degraded faster (7.76 +/- 0.08 x 10(-3) mmol EtOH/min-kg VSS) but did not have a noticeable effect on the rate of MTBE degradation. No evidence of TBA degradation was observed by the iron-reducing cultures. Stoichiometry of iron utilization was determined from the iron balance of the continuous-flow reactor, and it was found that the bulk of the electron acceptor was required for energy and maintenance with little remaining for cell synthesis. This is consistent with a yield coefficient of less than 0.1. Molecular analysis of the iron-reducing culture by denaturing gradient gel electrophoresis indicated that uncultured strains of delta-Proteobacteria were dominant in the reactor.