Impact of Chlorofluorocarbon 113 on Chlorinated Ethene Biodegradation

The inhibition of tetrachloroethene (PCE) degradation in anaerobic, ethanol-fed PCE-enrichment cultures by chlorofluorocarbon 113 (CFC113) was a function of the initial CFC113 concentration. Typically, aqueous CFC113 concentrations up to 1 mg/L slowed, but did not stop PCE-degradation, but cis-1,2-dichloroethene (cDCE) degradation was inhibited by 0.2 mg/L CFC113. In some cultures, however, PCE degradation was stopped by as little as 0.15 mg/L CFC113. CFC113 also slowed the consumption of hydrogen and the concurrent methane production. CFC113 slowly degraded in PCE-enrichment cultures to hydrochlorofluorocarbon 123a (HCFC123a). Chlorotrifluoroethene was also detected. Although relatively non-toxic, CFC113 may nevertheless pose remediation challenges when present at sites that also contain PCE.     

Anaerobic Microbial Reductive Dehalogenation of Chlorinated Ethenes

The current knowledge on microbial reductive dechlorination of chlorinated ethenes (CEs) and its application are discussed. Physiological studies on CEs dechlorinating microorganisms indicate that a distinction can be made between cometabolic dechlorination and halorespiration. Whereas cometabolic dechlorination is a coincidental and nonspecific side reaction, catalyzed by several methanogenic and acetogenic bacteria, halorespiration is a specific enzymatic reaction from which metabolic energy can be gained. In contrast to the well-studied biological dechlorination of PCE to cis-DCE, little is known about the biology of the further dechlorination from cis-DCE to ethene. Bacteria performing the latter reaction have not yet been isolated. Microbial reductive dechlorination can be applied to the in situ bioremediation of CEs contaminated sites. From laboratory and field studies, it has become clear that the dechlorination of tetrachloroethene (PCE) to cis-clichloroethene (cis-DCE) occurs rapidly and can be stimulated relatively easily. However, complete reduction to ethene appears to be a slower process that is more difficult to achieve.     

Bioenergetics and pathway of acid blue 113 degradation by Staphylococcus lentus

Bioreaction calorimetric studies of degradation of the dye acid blue 113 by Staphylococcus lentus are reported for the first time. The heat released during the dye degradation process can be successfully measured using reaction calorimeter. Power time and oxygen uptake rate (OUR) profile followed each other suggesting that heat profiles could monitor the progress of the dye degradation in biocalorimetry. The shifts observed in power–time profile indicated three distinct phases of the bioprocess indicating simultaneous utilization of glucose (primary) and dye (secondary carbon source). Secretion of azoreductase enzyme enhanced the degradation process. Optimization of aeration and agitation rates was observed to be vital to efficient dye degradation. The degradative pathway for acid blue 113 by S. lentus was delineated via high‐performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FT‐IR), and gas chromatography coupled with mass spectrometry (GC‐MS) analyses. Interestingly the products of degradation were found to have low toxicity, as per cytotoxicity measurements. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012     

Biodegradation of Residual Dense Nonaqueous-Phase Liquid Tetrachloroethene: Effects on Mass Transfer

The mass emissions rate of contaminants from nonaqueous-phase liquids (NAPLs) is a driving factor in remediation efforts, whether those efforts are designed to remove, transform, or stabilize the entrapped NAPL or down-gradient aqueous concentrations. Enhancement of mass flux from NAPL source zones has been previously reported in the presence of microbial reductive dechlorination activity in systems containing NAPL with a low proportion of tetrachloroethene (PCE) or a low residual saturation (e.g., 2%). The results reported here demonstrate reductive dechlorination of PCE at residual saturations of 35%, obtained under two different column flow velocities and NAPL configurations. Mass flux in biotic columns was approximately 45% greater than that in uninoculated columns, due to both the presence of daughter products and higher concentrations of PCE in the effluent from biotic columns. Daughter product concentrations were greater in columns with NAPL emplaced only in the lower quarter compared to those with NAPL throughout, and in columns run at the slower velocity. The elevated PCE concentrations in biotic column effluents suggest the influence of microbially generated surfactants, which was supported by surface tension measurements. These results demonstrate the potential significance of bioactivity within NAPL source zones on NAPL longevity and down-gradient aqueous concentrations.     

Aerobic and Anaerobic Biodegradation of Aged Pentachlorophenol by Indigenous Microorganisms

Pentachlorophenol (PCP) use as a general biocide, particularly for treating wood, has led to widespread environmental contamination. Biodegradation has emerged as the main mechanism for PCP degradation in soil and groundwater and a key strategy for remediation. Examining the microbial biodegrading potential for PCP at a contaminated site is crucial in determining its fate. Hundreds of studies have been published on PCP microbial degradation, but few have described the biodegradation of PCP that has been in contact with soils for many years. The bioavailability of “aged” hydrophobic organics is a significant concern. PCP- and 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP)-contaminated soil samples from several depths at a former wood treatment site were placed under varying conditions in the laboratory to determine the anaerobic and aerobic potential for biodegradation of chlorophenols at the site. PCP biodegradation occurred in both anaerobic and aerobic soil samples. Rapid aerobic degradation occurred in samples spiked with 2- and 4-chlorophenol, but not with 3-chlorophenol. Reductive dechlorination of PCP in anaerobic samples resulted in the accumulation of 3-chlorophenol. In most anaerobic replicates, 3-chlorophenol was degraded with the appearance of detectable, but not quantifiable amounts of phenol. These results indicate excellent potential for remediation at the site using the indigenous microorganisms under both aerobic and anaerobic conditions. However, a fraction of the PCP was unavailable for degradation.     

Application of 113Cd NMR to metallothioneins

Metallothioneins constitute a class of ubiquitously occurring low molecular mass proteins (6–7 kDa) possessing two cysteine thiolate-based metal clusters usually formed by the preferential binding of d10 metal ions such as Zn II and Cd II. The three-dimensional solution structure of mammalian proteins has been determined by two-dimensional NMR spectroscopy of 113Cd7-metallothionein. The structure shows two protein domains encompassing the M3(CysS)9- and M4(CysS)11-cluster with each metal ion being tetrahedrally coordinated by thiolate ligands. The application of 113Cd NMR proved to be indispensable in the structural studies of metallothioneins. Thus, both homonuclear 113Cd decoupling studies and 113Cd-113Cd COSY of 113Cd7-metallothionein established the existence of two metal-thiolate clusters in this protein. The identification of sequence specific cysteine-cadmium coordinative bonds came from heteronuclear 113Cd-1H COSY experiments. Independently, the 113Cd NMR characterization of the intermediate metal-protein complexes, leading to the cluster structure in 113Cd7- metallothionein, revealed a stepwise cluster formation process with the Cd4(CysS)11-cluster being formed first. The recent demonstration of a Karplus-like dependence between the heteronuclear 3J(113 Cd,1 H) coupling constants for the cysteine C protons and the H-C: -S -Cd dihedral angles should allow to derive the geometry of the Cd-(S-Cys) centers in various metallothioneins and related metalloproteins. A possible application of 113Cd NMR to the study of metallothioneins in the environment is discussed.     

Potential for Aerobic and Anaerobic Biodegradation of Petroleum Hydrocarbons in Boreal Subsurface

We studied the role of aerobic and anaerobic petroleum hydrocarbon degradation at a boreal, light-weight fuel and lubrication oil contaminated site undergoing natural attenuation. At the site, anoxic conditions prevailed with high concentrations of CH4 (up to 25% v/v) and CO2 (up to 18% v/v) in the soil gas throughout the year. Subsurface samples were obtained mainly from the anoxic parts of the site and they represented both the unsaturated and saturated zone. The samples were incubated in microcosms at near in situ conditions (i.e. in situ temperature 8 degrees C, aerobic and anaerobic conditions, no nutrient amendments) resulting in the removal of mineral oil (as determined by gas chromatography) aerobically as well as anaerobically. In the aerobic microcosms on average 31% and 27% of the initial mineral oil was removed during a 3- and 4-month incubation, respectively. In the anaerobic microcosms, on average 44% and 15% of the initial mineral oil was removed during a 12- and 10-month anaerobic incubation, respectively, and e.g. n-alkanes from C11 to C15 were removed. A methane production rate of up to 2.5 microg CH4 h(-1) g(-1) dwt was recorded in these microcosms. In the aerobic as well as anaerobic microcosms, typically 90% of the mineral oil degraded belonged to the mineral oil fraction that eluted from the gas chromatograph after C10 and before C15, while 10% belonged to the fraction that eluted after C15 and before C40. Our results suggest that anaerobic petroleum hydrocarbon degradation, including n-alkane degradation, under methanogenic conditions plays a significant role in the natural attenuation in boreal conditions.     

Biodegradation of the nitroaromatic herbicide dinoseb (2-sec-butyl-4,6-dinitrophenol) under reducing conditions

The degradation pathway for dinoseb (2-sec-butyl-4,6-dinitrophenol) under reducing conditions was investigated. Cultures were inoculated with a dinoseb-degrading anaerobic enrichment culture used in field studies. Biotransformation intermediates were extracted with ethyl acetate and analyzed by high pressure liquid chromatography, gas chromatography, and mass spectrometry. Dinoseb degradation involves reduction of the nitro groups to amino groups followed by replacement with hydroxyl groups. Depending on the pH and redox potential in the culture, these intermediates may exist as quinones or hydroquinones.Publication No. 94506 of the Idaho Agricultural Experiment Station     

棉花Lea蛋白D-113基因启动子的克隆及序列分析

为研究植物Lea(late embryogenesis abundant）蛋白基因启动子在种子中的特异性表达,通过PCR扩增,从棉花（Gossypium hirsutum cv.Coker312）中克隆了Lea蛋白基因家庭中D-113基因上游1024bp的调控序列。DNA序列分析结果表明,该片段与已报道的Lea蛋白基因同一家庭该基因的对应序列同源性达90%以上。将将启动子序列与GUS基因融合,构建成表达载体后,通过基因抢轰击导入到经ABA诱导处理的棉花胚性愈伤组织和油菜种子以及棉花的根、茎、叶中,组织化学分析结果表明,D-113基因启动子在胚中特异性表达。     

Effect of Chlorinated Ethene Conversion on Viability and Activity of Methylosinus trichosporium OB3b

The effect of transformation of chlorinated ethenes on the cell viability of Methylosinus trichosporium OB3b was investigated. A comparison of the loss of viability with the decrease in transformation rates showed that for the monooxygenase-mediated transformation of all chlorinated ethenes except vinyl chloride the decrease in cell viability was the predominant toxic effect.     

Biodegradation of Malathion with Indigenous Acclimated Activated Sludge in Batch Mode and in Continuous-Flow Packed-Bed Reactor

Acclimated activated sludge was examined for its ability to degrade malathion with and without the presence of glucose as a potential cometabolite substrate. In this study, a packed-bed reactor (PBR) using three kinds of biofilm carriers was employed for efficient degradation of malathion. The results obtained indicate that microorganisms tested were able to degrade malathion. The observed degradation rate of the pesticide in the presence of glucose was the same as without glucose. The activated sludge was found to be able to use malathion as the sole phosphorus source. In contrast, the degradation ability of the activated sludge was lost when the pesticide was used as the sole source of sulfur. The degradation capacity of the PBR was higher than the performance obtained with the batch reactor. The reactor packed with crushed olive kernels exhibited the best performance, allowing a total removal of malathion (10 mg/dm³) within 12 h.     

Role of sulfate in microbial transformations of environmental contaminants: Chlorinated aromatic compounds

Despite recent progress made in describing microbial transformations that occur under anaerobic conditions, our understanding of the role sulfate‐reducing bacteria may play in the remediation of environmental contaminants is still very limited. The objective of this mini‐review is to summarize what is currently known of the metabolism of chlorinated aromatic compounds in the presence of sulfate. Sulfidogenic processes are discussed with respect to the thermodynamics of haloaromatic oxidation and to their potential use in the in situ bioremediation of hazardous organic wastes. A comprehensive listing is made of anaerobic transformations that involve both halogenated and nonhalogenated monoaromatic substrates by denitrifiers, dissimilatory iron‐reducing bacteria, and methanogenic consortia. In contrast to other anaerobic processes, studies involving sulfate‐mediated metabolism of hazardous organic compounds have been neglected; however, the recent success in defining methanogenic transformations, in particular, has enhanced expectations of defining an analogous role for sulfate‐reducing microbial communities in low redox environments that have become contaminated with hazardous substances.     

Biodegradation of lignin-carbohydrate complexes

Covalent lignin-carbohydrate (LC) linkages exist in lignocellulose from wood and groups herbaceous plants. In wood, they consist of ester and ether linkages through sugar hydroxyl to the -carbanol of phenylpropane subunits in lignin. In grasses, ferulic and p-coumaric acids are esterified to hemicelluloses and lignin, respectively. Hemicelluloses also contain substitutents and side groups that restrict enzymatic attack. Watersoluble lignin-carbohydrate complexes (LCCs) often precipitate during digestion with polysaccharidases, and the residual sugars are more diverse than the bulk hemicellulose. A number of microbial esterases and hemicellulose polysaccharidases including acetyl xylan esterase, ferulic acid esterase, and p-coumaric esterase attack hemicellulose side chains. Accessory hemicellulases include -l-arabinofuranosidase and -methyl-glucuranosidase. Both of these side chains are involved in LC bonds. -Glucosidase will attach sugar residues to lignin degradation products and when carbohydrate is attached to lignin, lignin peroxidase will depolymerize the lignin more readily.Abbreviations APPL acid precipitable polymeric lignin - CBQase cellobioquinone oxidoreductase - LC lignincarbohydrate - LCC(s) lignin-carbohydrate complex - DHP Dehydrogenative polymerisate - DMSO dimethylsulfoxide - DP degree of polymerisation - MWEL milled wood enzyme lignin - MWL milled wood lignin (not digested with carbohydrases)     

Biodegradation of phenol and cresol isomer mixtures by Arthrobacter

The Arthrobacter species can degrade phenol, o-cresol and p-cresol much faster (as reflected in high specific growth rates) than other microbes which are reported to degrade toxic compounds. In mixtures, phenol and p-cresol mutually inhibited each other; the inhibition constants show that phenol degradation is strongly inhibited in the presence of p-cresol rather than reverse. o-Cresol enhanced phenol degradation marginally but o-cresol degradation was not affected by the presence of phenol.     

石油污染土壤的生物降解研究

石油工业迅速的发展带来了许多环境问题。在原油生产与输送过程中[1] ,井喷、泄露及沉降排放等引起的原油进入土壤造成的土壤污染 ,很难治理。原油在环境中残留时间长 ,对土壤微生物和土壤 植物生态系统 ,甚至地下水都产生危害 ,影响土壤肥力 ,破坏土壤生产力 ,严重影响当地的粮食产量及产品质量。当前 ,治理土壤石油污染的方法主要有物理法、化学法和生物治理技术[2 ] 。污染土壤生物清洁技术就是利用微生物将土壤中有害有机污染物降解为无害无机物 (ＣＯ2 和Ｈ2 Ｏ)的过程。降解过程可以由改变土壤理化条件 (包括土壤ｐＨ ,温度、湿度、…     

The Impact of H2 Addition on Dechlorinating Microbial Communities

Laboratory-scale column experiments were performed to investigate the effects of membrane-supplied H₂ on tetrachloroethene (PCE) dechlorination and microbial community composition. Columns were filled with aquifer material from one of two TCE-contaminated sites and fed a PCE-spiked anaerobic minimal medium for approximately 1 year. For each experiment, one or more experimental columns were supplied with H₂ via gas-permeable hollow-fiber membranes with one control column not receiving any H₂. After approximately 1 year of operation, aquifer material samples were collected along the length of the columns. Bacterial communities in the samples were analyzed by amplifying the highly variable V3 region of the 16S rRNA gene and separating amplicons using denaturing gradient gel electrophoresis. Microbial community profiles in H₂-fed (continuous or pulsed delivery) columns were compared with those in untreated control columns and microbial community profiles were also compared with dechlorination profiles. Selected bands were sequenced for identification. Supply of the simple electron donor H₂, changed the microbial community composition, but did not decrease overall diversity. Continuous H₂ addition via hollow-fiber membranes enriched for Dehalococcoides-like species, whose relative abundance correlated with enhanced dechlorination activity. PCE was completely dechlorinated to ethene in columns packed with aquifer material from Cape Canaveral, Florida; PCE was dechlorinated to only cis-dichloroethene, however, in columns packed with aquifer material from a TCE-contaminated wetland near Minneapolis, Minnesota. Unexpectedly, Dehalococcoides-like populations were detected in samples from both sets of column experiments. These results suggest that the mere detection of Dehalococcoides-like species in a sample of aquifer material is not a sufficient indicator of the potential to dechlorinate PCE to ethene via biostimulation by H₂.     

芫菁寄生菌降解斑蝥素

选用2种芫菁的寄生菌——球孢白僵菌Beauveria bassiana和曲霉Aspergillus sp.,进行斑蝥素的抑菌试验和对斑蝥素的降解试验。结果表明:斑蝥素对这2种真菌没有抑制作用,球孢白僵菌可以有效地降解斑蝥素,降解率为90.45%,而曲霉不能降解斑蝥素。     

Stable carbon isotope signatures of background tropospheric chloromethane and CFC113

Samples of background air were collected in thelower troposphere of the Northern (high Arctic,northern Ontario, Vancouver and Houston) andSouthern (Baring Head, New Zealand) Hemispheresover the period July 1999 until March 2001.These samples were analysed for the stablecarbon isotope ratios of1,1,1-trichlorotrifluoroethane (CFC113) andCH₃Cl using a gaschromatography-continuous flow on-linecombustion isotope ratio mass spectrometrycombination. For CH₃Cl the global averageof the stable carbon isotope ratio is –36.2± 0.3 (error of mean). The average isbased on 78 data points, standard deviation forall measurements is 2.3, and the 90%confidence interval is –35.8 to –36.6.However, the number of data points from theSouthern Hemisphere is rather limited and thusthis observation is not necessarilyrepresentative for the entire SouthernHemisphere. A simple isotopic budget ofCH₃Cl shows the most important parametersneeding to be defined are the kinetic isotopeeffect of CH₃Cl destruction by OH radicalsand the source composition of CH₃Clemitted by the oceans and biomass burning ofC-4 plants. Present budgets of atmosphericCH₃Cl show a significant deficit in thesource strength. We estimate that the averagestable carbon isotope ratio of the additionalCH₃Cl emissions required to balance thebudget is –41.9 ± 7.8. The averageCFC113 isotopic composition based on 38measurements is –23.3 ± 1.6 (error ofmean), = 9.6 with no significantdifference between the hemispheres.