Anaerobic biodegradation of 1,4-dioxane by sludge enriched with iron-reducing microorganisms

The potential on anaerobic biodegradation of 1,4-dioxane was evaluated by use of enriched Fe(III)-reducing bacterium sludge from Hangzhou municipal wastewater treatment plant. The soluble Fe(III) supplied as Fe(III)-EDTA was more available for the Fe(III)-reducing bacterium in the sludge compared to insoluble Fe(III) oxide. The addition of humic acid (HA) further stimulated the anaerobic degradation of 1,4-dioxane accompanying with apparent reduction of Fe(III) which is believed that HA could stimulate the activity of Fe(III)-reducing bacterium by acting as an electron shuttle between Fe(III)-reducing bacterium and Fe(III), especially for insoluble Fe(III) oxides. After 40-day incubation, the concentration of 1,4-dioxane dropped up to 90% in treatment of Fe(III)-EDTA+HA. Further study proved that more than 50% of the carbon from 1,4-dioxane was converted to CO2 and no organic products other than biomass accumulated in the growth medium. The results demonstrated that, under the appropriate conditions, 1,4-dioxane could be biodegraded while serving as a sole carbon substrate for the growth of Fe(III)-reducing bacterium. It might be possible to design strategies for anaerobic remediation of 1,4-dioxane in contaminated subsurface environments.     

Evaluation of the biodegradation potential of 1,4-dioxane in river, soil and activated sludge samples

To evaluate the biodegradation potential of 1,4-dioxane in natural environments, a total of 20 environmental samples including river water, activated sludge, soil from the drainage area of a chemical factory and garden soil were subjected to a 1,4-dioxane degradation test. The five soil samples from the drainage area of the chemical factory were capable of reducing 100 mg l^?1 of 1,4-dioxane to below the detection limit (0.8 mg l^?1) within 33 days. In one activated sludge sample, 100 mg l^?1 of 1,4-dioxane decreased by 69% within 14 days via cometabolic degradation in the presence of 100 mg l^?1 of tetrahydrofuran (THF). The ability of all samples to degrade 1,4-dioxane degradation with or without THF increased after repeated enrichment, except for one soil sample from the drainage area of the chemical factory that was no longer able to degrade 1,4-dioxane after the third cycle of enrichment. However, most of the samples (14/20) were not able to degrade 1,4-dioxane degradation. Thus, it can be concluded that the potential for 1,4-dioxane degradation is not ubiquitously distributed in natural environment.     

Potential for anaerobic bioremediation of BTEX in petroleum-contaminated aquifers

Laboratory incubations of aquifer material or enrichments derived from aquifer material as well as geochemical data have suggested that, under the appropriate conditions, BTEX components of petroleum (benzene, toluene, ethylbenzene and xylene) can be degraded in the absence of molecular oxygen with either Fe(III), sulfate, or nitrate serving as the electron acceptor. BTEX degradation under methanogenic conditions has also been observed. However, especially for benzene, the BTEX contaminant of greatest concern, anaerobic degradation is often difficult to establish and maintain in laboratory incubations. Although studies to date have suggested that naturally occurring anaerobic BTEX degradation has the potential to remove significant quantities of BTEX from petroleum-contaminated aquifers, and mechanisms for stimulating anaerobic BTEX degradation in laboratory incubations have been developed, further study of the organisms involved in this metabolism and the factors controlling their distribution and activity are required before it will be possible to design rational strategies for accelerating anaerobic BTEX degradation in contaminated aquifers. Received 21 November 1995/ Accepted in revised form 20 February 1996     

Degradation of 1,4-dioxane by an actinomycete in pure culture.

An actinomycete capable of sustained aerobic growth on 1,4-dioxane was isolated from a dioxane-contaminated sludge samples. The actinomycete, CB1190, grows on 1,4-dioxane as the sole carbon and energy source with a generation time of approximately 30 h. CB1190 degrades 1,4-dioxane at a rate of 0.33 mg of dioxane min-1 mg of protein-1 and mineralizes 59.5% of the dioxane to CO2. CB1190 also grows with other cyclic and linear ethers as the sole carbon and energy sources, including 1,3-dioxane, 2-methyl-1,3-dioxolane, tetrahydrofuran, tetrahydropyran, diethyl ether, and butyl methyl ether. CB1190 is capable of aerobic autotrophic growth on H2 and CO2.     

Mineralization of 1,4-dioxane in the presence of a structural analog

A mixed culture with the ability to aerobically biodegrade 1,4-dioxane in the presence of tetrahydrofuran (THF) was enriched from a 1,4-dioxane contaminated aquifer. This consortium contained 3–4 morphologically different types of colonies and was grown in mineral salts media. Biodegradation of 1,4- dioxane began when THF concentrations in batch experiments became relatively low. No biodegradation of 1,4-dioxane was observed in the absence of THF and the measured cell yield was similar during degradation of 1,4-dioxane with THF or with THF alone. However, when the consortium was grown in the presence of ¹⁴C-1,4-dioxane plus THF, 2.1% of the radiolabeled 1,4-dioxane was present in the particulate fraction. The majority of the ¹⁴C (78.1%) was recovered as ¹⁴CO₂, while 5.8% remained in the liquid fraction. This activity is interesting since the non-growth substrate is mineralized, yet only minimally assimilated into biomass. Using THF as the growth substrate, 1,3-dioxane, methyl t-butyl ether, ethyl t-butyl ether and t-amyl methyl ether.     

Different utilizable substrates have different effects on cometabolic fate of imidacloprid in Stenotrophomonas maltophilia

Imidacloprid, the largest selling insecticide in the world, is more stable in soil, and its environmental residue and effects are attracting people's close attention. One of imidacloprid metabolism pathways was degraded to CO₂ through olefin imidacloprid pathway. Here, we report that sucrose as a utilizable substrate enhanced the cometabolism of imidacloprid by Stenotrophomonas maltophilia CGMCC 1.1788 to produce 5-hydroxy imidacloprid, whereas when succinate was used as a utilizable substrate, 5-hydroxy imidacloprid from imidacloprid was transformed to olefin imidacloprid, and the latter was further degraded. The hydroxylation of imidacloprid required NAD(P)H, whereas the dehydration of 5-hydroxy imidacloprid to form olefin imidacloprid required succinate rather than NAD(P)H. NADPH greatly favored the hydroxylation of imidacloprid more than NADH, and NADPH inhibited the dehydration of 5-hydroxy imidacloprid to olefin imidacloprid, but NADH did not. Therefore, sucrose may be metabolized through hexose monophosphate pathway to produce mainly NADPH which participated in the hydroxylation of imidacloprid to 5-hydroxy imidacloprid and meanwhile inhibited the dehydration of 5-hydroxy imidacloprid to olefin imidacloprid, whereas succinate may be metabolized mainly through the tricarboxylic acid cycle to produce NADH which was involved in hydroxylation of imidacloprid to 5-hydroxy imidacloprid but did not inhibit the dehydration of 5-hydroxy imidacloprid to olefin imidacloprid. Our results have a significant meaning in further understanding the influence of different utilizable substrates on the cometabolic pathways and the fate of environmental imidacloprid.     

Co-metabolic biodegradation of trichloroethylene by Methylosinus trichosporium is stimulated by low concentrations methane or methanol

Co-metabolic biodegradation of trichloroethylene by Methylosinus trichosporium OB3b was stimulated by low concentrations of methane (up to 70 M) or methanol (up to 0.4 mM) but inhibited at higher concentrations of them. A kinetic equation describing the dual effects of methane or methanol is proposed and the relevant kinetic constants have been determined.     

Soluble chromogenic substrates for the assay of endo-1,4-beta-xylanases and endo-1,4-beta-glucanases

New soluble chromogenic substrates were prepared for specific and rapid assays of endo-1,4-beta-xylanases and endo-1,4-beta-glucanases. A soluble beechwood 4-O-methyl-D-glucurono-D-xylan was dyed with Remazol brilliant blue R, and hydroxyethylcellulose was coupled to Ostazin brilliant red H-3B. The assays are based on photometric measurements of the enzyme-released dyed fragments soluble in the presence of organic solvents which precipitate the original substrates and their high-molecular-weight fractions. The assays are advantageous for rapid analyses of large amount of samples and also permit evaluation of the activities of both enzymes in the presence of exo-beta-glycanases and beta-glycosidases, at a high level of reducing compounds and viable cells, on the cell surface and on cell membranes and organelles.     

Specificity of rabbit muscle phosphofructokinase for nucleotides as substrates or as allosteric effectors.

Various ATP and AMP analogs with modifications in the base moiety or in the polyphosphate chain were tested as substrates and/or as allosteric effectors of rabbit muscle phosphofructokinase. The significance of different structural elements for the nucleotide-enzyme interaction is discussed. While all investigated triphosphate analogs with a modified purine base are substrates for phosphofructokinase, those with a modified polyphosphate chain are competitive inhibitors. 5′-Adenylyl-(β,γ-methylene) diphosphonate, which is a weak competitive inhibitor, is shown to have a high affinity for the allosteric site of phosphofructokinase. Among the investigated monophosphate analogs only adenosine-N¹-oxide 5′-monophosphate can reverse the inhibitory effect of excessive ATP. A qualitative correlation is found between the quenching of the phospho-fructokinase-8-anilino-1-naphthalene-sulfonate fluorescence and the ability of the nucleotide analogs to act as substrates or as allosteric effectors of phosphofructokinase. It is concluded that the interaction of ATP with the allosteric site is more complex than that with the substrate site and requires both an intact adenine moiety and an intact terminal phosphate group for full activity.     

Role of competition for inorganic nutrients in the biodegradation of mixtures of substrates.

A study was conducted to determine whether competition for inorganic nutrients affects the biodegradation of mixtures of substrates. Little benzylamine was mineralized by Pseudomonas putida in solutions with no added P, but the substrate was degraded if the medium contained 100 nM P. The enhancement by P addition did not occur if the medium also contained caprolactam and a caprolactam-utilizing strain of Pseudomonas aeruginosa. The suppression by the second bacterium was overcome by a higher P concentration. The rate of caprolactam utilization by P. aeruginosa was reduced if benzylamine and P. putida were also present in media with 100 nM P, but the suppression was absent if the solution contained a higher P concentration. Glutamate increased and inorganic N plus P decreased the length of the acclimation phase prior to benzylamine mineralization in lake water. We suggest that the effect of one biodegradable substrate on the metabolism of a second often results from a competition for inorganic nutrients.     

Ab initio and dielectric studies of succinic acid and maleic acid in 1,4-dioxane

In a continuing effort to understand the hydrogen bond through the study of dielectric and computational conformal studies of dilute solutions, succinic acid and maleic acid are studied in solutions of 1,4-dioxane solvent. Dielectric studies give an account of the net dipole moment of the system under study, which is then compared with the values obtained from conformal analysis. The dielectric measurements were made at 303 K at a frequency of 9.83 GHz using a X-band microwave test bench in order to determine the relaxation times and the dipole moments. The static dielectric permittivity and the high frequency dielectric permittivity were measured using a LCR meter and an Abbe's refractometer, respectively. The results are inspected in comparison with the dipole moment results of ab initio calculations of some of the conformers in gas phase and in liquid phase. Gaussian-03 software package with 6–31G(d) basis set optimisation was used for this purpose. Onsager's reaction field model is used to study the solvation of the dicarboxylic acids in 1,4-dioxane. The results are interpreted in terms of the intermolecular and intramolecular hydrogen bond interactions in the dilute systems.     

Potential for biodegradation of hydrocarbons by microorganisms isolated from Antarctic soils

Seventeen pure aerobic microbial isolates were obtained from soil samples of three regions of Antarctica: Casey Station, Dewart Island and Terra Nova Bay. Most of them were gram positive coryneform bacteria. Isolates were tested for their ability to grow on mineral salt agar plates supplemented with one of the following model n-alkanes or aromatic hydrocarbons: hexane, heptane, paraffin, benzene, toluene, naphthalene and kerosene. Cell hydrophobicity, the ability to produce anionic glycolipids and extracellular emulsifying activity were also determined and assessed on the basis of growth of soil isolates on hydrocarbons. This study revealed degraders with broader abilities to grow on both types of hydrocarbons, good production of glycolipids and emulsifying activity. On this basis, a mixed culture of strains is proposed, which may find application for bioremediation at temperate temperature of soil environments polluted with different hydrocarbons.     

Synthesis of Some New 1,3/ or 1,4-Bis(Glucopyranosyl-1,2,4-Triazol-5-Ylthio)Propanes/ or Butanes as Potential Antimicrobial Agents

Glucosidation of the appropriate 1,3 or 1,4-bis(4-amino or arylideneamino-2,4-dihydro-3-thioxo-3H-1,2,4-triazol-5-ylthio)propanes or butanes with 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl bromide followed by chromatographic separation gave the corresponding N-, S-, and N,S-bis(glucosides). Chemical transformation leading to new functionalities has been achieved. Antimicrobial screening of 10 selected compounds resulted in their activity against Aspergillus fumigatus, Penicillium italicum, Syncephalastrum racemosum, Candida albicans, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis, and Escherichia coli.     

Potential for methane production from anaerobic co-digestion of swine manure with winery wastewater

This work examines the methane production potential for the anaerobic co-digestion of swine manure (SM) with winery wastewater (WW). Batch and semi-continuous experiments were carried out under mesophilic conditions. Batch experiments revealed that the highest specific methane yield was 348 mL CH₄ g⁻¹ COD added, obtained at 85.4% of WW and 0.7 g COD g⁻¹ VS. Specific methane yield from SM alone was 27 mL CH₄ g⁻¹ COD added d⁻¹. Furthermore, specific methane yields were 49, 87 and 107 mL CH₄ g⁻¹ COD added d⁻¹ for the reactors co-digesting mixtures with 10% WW, 25% WW and 40% WW, respectively. Co-digestion with 40% WW improved the removal efficiencies up to 52% (TCOD), 132% (SCOD) and 61% (VSS) compared to SM alone. These results suggest that methane can be produced very efficiently by the co-digestion of swine manure with winery wastewater.     

Potential for biodegradation of hydrocarbons in soil from the Ross Dependency, Antarctica

Oil spills occur in the Antarctic when fuel oils such as JP8 jet fuel are moved or stored. Hydrocarbons, both n-alkanes and aromatic compounds, have been detected in oil-contaminated soils of the Ross Dependency. In such areas hydrocarbon-degrading microbes, if naturally occurring, could be used for clean-up. Soil samples from oil-impacted and control sites were analysed for hydrocarbon-degrading microbes and for a range of parameters known to limit biodegradative activity. Soils were analysed for water content, pH, concentrations of nutrients (N and P) and electrical conductivity. Numbers of culturable heterotrophic bacteria and hydrocarbon degraders were greater in some of the oil-contaminated samples. Mineralisation studies with ¹⁴C-radiolabelled hexadecane and naphthalene demonstrated that nitrogen amendments significantly enhanced hydrocarbon mineralisation rates in an oil-impacted soil. Received: 30 June 1997 / Received revision: 15 September 1997 / Accepted: 19 September 1997