Delignified porous wood as biofilm support for 1,4-dioxane-degrading bacterial consortium

Delignified porous wood samples were used as carriers for biofilm formation of a bacterial consortium with the ability to degrade 1,4-dioxane (DX). The delignification treatment of the natural wood resulted in higher porosity, formation of macropores, increase in surface roughness and hydrophilicity of the treated wood pieces. These superior properties of two types of treated carriers (respectively, A and B) compared to the untreated wood resulted in 2.19 ± 0.52- and 2.66 ± 0.23-fold higher growth of biofilm. Moreover, analysis of the fatty acid profiles indicated an increase in proportion of the saturated fatty acids during the biofilm formation, characterising an enhancement in rigidity and hydrophobicity of the biofilms. DX initial concentration of 100 mg/L was completely degraded (detection limit 0.01 mg/L) in 24 and 32 h using the treated A and B woods, while only 25.84 ± 5.95% was removed after 32 h using the untreated wood. However, fitting the DX biodegradation data to the Monod model showed a lower maximum specific growth rate for biofilm (0.0276 ± 0.0018 1/h) versus planktonic (0.0382 ± 0.0024 1/h), because of gradual accumulation of inactive cells in the biofilm. Findings of this study can contribute to the knowledge of biofilm formation regarding the physical/chemical properties of biofilm carriers and be helpful to the ongoing research on bioremediation of DX.

Self-assembling a 1,4-dioxane-degrading consortium and identifying the key role of Shinella sp. through dilution-to-extinction and reculturing

IMPORTANCE

Assembling a functional microbial consortium and identifying key degraders involved in the degradation of 1,4-dioxane are crucial for the design of synergistic consortia used in enhancing the bioremediation of 1,4-dioxane-contaminated sites. However, due to the vast diversity of microbes, assembling a functional consortium and identifying novel degraders through a simple method remain a challenge. In this study, we reassembled 1,4-dioxane-degrading microbial consortia using a simple and easy-to-operate method by combining dilution-to-extinction and reculture techniques. We combined differential analysis of community structure and metabolic function and confirmed that Shinella species have a stronger 1,4-dioxane degradation ability than Xanthobacter species in the enriched consortium. In addition, a new dioxane-degrading bacterium was isolated, Shinella yambaruensis, which verified our findings. These results demonstrate that DTE and reculture techniques can be used beyond diversity reduction to assemble functional microbial communities, particularly to identify key degraders in contaminant-degrading consortia.

Dual phytoremediation and biochar production by Eichhornia crassipes in hydroponic system receiving different 1,4-dioxane dosages

This study focuses on applying phytoremediation as a low-effective and simple process to treat wastewater laden with 1,4 dioxane (DIOX). A floating macrophyte (Eichhornia crassipes) was cultivated under hydroponic conditions (relative humidity 50-67%, photoperiod cycle 18:6 h light/dark, and 28-33 °C) and subjected to different DIOX loads between 0.0 (control) and 11.5 mg/g fresh mass (FM). The aquatic plant achieved DIOX and chemical oxygen demand (COD) removal efficiencies of 76-96% and 67-94%, respectively, within 15 days. E. crassipes could tolerate elevated DIOX-associated stresses until a dose of 8.2 mg DIOX/g, which highly influenced the oxidative defense system. Malondialdehyde (MDA) content, hydrogen peroxide (H2O2), and total phenolic compounds (TPC) increased by 7.3, 8.4, and 4.5-times, respectively, in response to operating the phytoremediation unit at a DIOX load of 11.5 mg/g. The associated succulent value, proteins, chlorophyll-a, chlorophyll-b, and pigments dropped by 39.6%, 45.8%, 51.5%, 80.8%, and 55.5%, respectively. The suggested removal mechanism of DIOX by E. crassipes could be uptake followed by phytovolatilization, whereas direct photodegradation from sunlight contributed to about 19.36% of the total DIOX removal efficiencies. Recycling the exhausted E. crassipes for biochar production was a cost-efficient strategy, making the payback period of the phytoremediation project equals to 6.96 yr.

1,4-Dioxane removal in nitrifying sand filters treating domestic wastewater: Influence of water matrix and microbial inhibitors

1,4-Dioxane is a recalcitrant pollutant in water and is ineffectively removed during conventional water and wastewater treatment processes. In this study, we demonstrate the application of nitrifying sand filters to remove 1,4-dioxane from domestic wastewater without the need for bioaugmentation or biostimulation. The sand columns were able to remove 61 ± 10% of 1,4-dioxane on average (initial concentration: 50 μg/L) from wastewater, outperforming conventional wastewater treatment approaches. Microbial analysis revealed the presence of 1,4-dioxane degrading functional genes (dxmB, phe, mmox, and prmA) to support biodegradation being the dominant degradation pathway. Adding antibiotics (sulfamethoxazole and ciprofloxacin), that temporarily inhibited the nitrification process during the dosing period, showed a minor effect in 1,4-dioxane removal (6-8% decline, p < 0.05), suggesting solid resilience of the 1,4-dioxane-degrading microbial community in the columns. Columns amended with sodium azide significantly (p < 0.05) depressed 1,4-dioxane removal in the early stage of dosing but followed by a gradual increase of the removal over time to >80%, presumably due to a shift in the microbial community toward azide-resistant 1,4-dioxane degrading microbes (e.g., fungi). This study demonstrated for the first time the resilience of the 1,4-dioxane-degrading microorganisms during antibiotic shocks, and the selective enrichment of efficient 1,4-dioxane-degrading microbes after azide poisoning. Our observation could provide insights into designing better 1,4-dioxane remediation strategies in the future.

Electron donor addition for stimulating the microbial degradation of 1,4 dioxane by sequential batch membrane bioreactor: A techno-economic approach

The presence of 1,4 dioxane in wastewater is associated with severe health and environmental issues. The removal of this toxic contaminant from the industrial effluents prior to final disposal is necessary. The study comprehensively evaluates the performance of sequential batch membrane bioreactor (MBR) for treating wastewater laden with 1,4 dioxane. Acetate was supplemented to the wastewater feed as an electron donor for enhancing and stimulating the microbial growing activities towards the degradation of 1,4 dioxane. The removal efficiency of 1,4 dioxane was maximized to 87.5 ± 6.8% using an acetate to dioxane (A/D) ratio of 4.0, which was substantially dropped to 31.06 ± 3.7% without acetate addition. Ethylene glycol, glyoxylic acid, glycolic acid, and oxalic acid were the main metabolites of 1,4 dioxane biodegradation using mixed culture bacteria. The 1,4 dioxane degrading bacteria, particularly the genus of Acinetobacter, were promoted to 92% at the A/D ratio of 4.0. This condition encouraged as well the increase of the main 1,4 dioxane degraders, i.e., Xanthomonadales (12.5%) and Pseudomonadales (9.1%). However, 50% of the Sphingobacteriales and 82.5% of Planctomycetes were reduced due to the inhibition effect of the 1,4 dioxane contaminate. Similarly, the relative abundance of Firmicutes, Verrucomicrobia, Chlamydiae, Actinobacteria, Chloroflexi, and Nitrospirae was reduced in the MBR at the A/D ratio of 4.0. The results derived from the microbial analysis and metabolites detection at different A/D ratios indicated that acetate supplementation (as an electron donor) maintained an essential role in encouraging the microorganisms to produce the monooxygenase enzymes responsible for the biodegradation process. Economic feasibility of such a MBR system showed that for a designed flow rate of 30 m³∙d^-1, the payback period from reusing the treated wastewater would reach 6.6 yr. The results strongly recommend the utilization of mixed culture bacteria growing on acetate for removing 1,4 dioxane from the wastewater industry, achieving dual environmental and economic benefits.

Remedial strategies for abating 1,4-dioxane pollution-special emphasis on diverse biotechnological interventions

1,4-dioxane is a heterocyclic ether used as a polar industrial solvent and are released as waste discharges. 1,4-dioxane deteriorates health and quality, thereby attracts concern by the environment technologists. The need of attaining sustainable development goals have resulted in search of an eco-friendly and technically viable treatment strategy. This extensive review is aimed to emphasis on the (a) characteristics of 1,4-dioxane and their occurrence in the environment as well as their toxicity, (b) remedial strategies, such as physico-chemical treatment and advanced oxidation techniques. Special reference to bioremediation that involves diverse microbial strains and their mechanism are highlighted in this review. The role of macronutrients, stimulants and other abiotic cofactors in the biodegradation of 1,4-dioxane is discussed lucidly. We have critically discussed the inducible enzymes, enzyme-based remediation, distinct instrumental method of analyses to know the fate of intermediates produced from 1,4-dioxane biotransformation. This comprehensive survey also tries to put forth the different toxicity assessment tools used in evaluating the extent of detoxification of 1,4-dioxane achieved through biotransforming mechanism. Conclusively, the challenges, opportunities, techno-economic feasibility and future prospects of implementing 1,4-dioxane through biotechnological interventions are also discussed.

Network and meta-omics reveal the cooperation patterns and mechanisms in an efficient 1,4-dioxane-degrading microbial consortium

1,4-Dioxane is an emerging wastewater contaminant with probable human carcinogenicity. Our current understanding of microbial interactions during 1,4-dioxane biodegradation process in mixed cultures is limited. Here, we applied metagenomic, metatranscriptomic and co-occurrence network analyses to unraveling the microbial cooperation between degrader and non-degraders in an efficient 1,4-dioxane-degrading microbial consortium CH1. A 1,4-dioxane-degrading bacterium, Ancylobacter polymorphus ZM13, was isolated from CH1 and had a potential of being one of the important degraders due to its high relative abundance, highly expressed monooxygenase genes tmoABCDEF and high betweenness centrality of networks. The strain ZM13 cooperated obviously with 6 bacterial genera in the network, among which Xanthobacter and Mesorhizobium could be involved in the intermediates metabolism with responsible genes encoding alcohol dehydrogenase (adh), aldehyde dehydrogenase (aldh), glycolate oxidase (glcDEF), glyoxylate carboligase (gcl), malate synthase (glcB) and 2-isopropylmalate synthase (leuA) differentially high-expressed. Also, 1,4-dioxane facilitated the shift of biodiversity and function of CH1, and those cooperators cooperated with ZM13 in the way of providing amino acids or fatty acids, as well as relieving environmental stresses to promote biodegradation. These results provide new insights into our understandings of the microbial interactions during 1,4-dioxane degradation, and have important implications for predicting microbial cooperation and constructing efficient and stable synthetic 1,4-dioxane-degrading consortia for practical remediation.

Response surface algorithm for improved biotransformation of 1,4-dioxane using Staphylococcus capitis strain AG

The present investigation reports the biotransformation of an endrocrine disrupting agent; 1,4-dioxane through bacterial metabolism. Initially, potential bacterial isolates capable of surviving with minimum 1,4-dioxane were screened from industrial wastewater. Thereafter, screening was done to isolate a bacteria which can biotransform higher concentration (1000 mg/L) of 1,4-dioxane. Morphological and biochemical features were examined prior establishing their phylogenetic relationships and the bacterium was identified as Staphylococcus capitis strain AG. Biotransformation experiments were tailored using response surface tool and predictions were made to elucidate the opimal conditions. Critical factors influencing bio-transformation efficiency such as tetrahydrofuran, availability of 1,4-dioxane and inoculum size were varied at three different levels as per the central composite design for ameliorating 1,4-dioxane removal. Functional attenuation of 1,4-dioxane by S. capitis strain AG were understood using spectroscopic techniques were significant changes in the peak positions and chemical shifts were visualized. Mass spectral profile revealed that 1.5 (% v/v) S. capitis strain AG could completely (∼99%) remove 1000 mg/L 1,4-dioxane, when incubated with 2 μg/L tetrahydrofuran for 96 h. The toxicity of 1,4-dioxane and biotransformed products by S. capitis strain AG were tested on Artemia salina. The results of toxicity tests revealed that the metabolic products were less toxic as they exerted minimal mortality rate after 48 h exposure. Thus, this research would be the first to report the response prediction and precise tailoring of 1,4-dioxane biotransformation using S. captis strain AG.

Effect of biostimulation and bioaugmentation on biodegradation of high concentrations of 1,4-dioxane

1,4-Dioxane is a pervasive and persistent contaminant in numerous aquifers. Although the median concentration in most contaminant plumes is in the microgram per liter range, a subset of sites have contamination in the milligram per liter range. Most prior studies that have examined 1,4-dioxane concentrations in the hundreds of milligrams per liter range have been performed with industrial wastewater. The main objective of this study was to evaluate aerobic biodegradation of 1,4-dioxane in microcosms prepared with soil and groundwater from a site where concentrations range from ~ 1500 mg·L^-1 in the source zone, to 450 mg·L^-1 at a midpoint of the groundwater plume, and to 6 mg·L^-1 at a down-gradient location. Treatments included biostimulation with propane, addition of propane and a propanotrophic enrichment culture (ENV487), and unamended. The highest rates of biodegradation for each location in the plume occurred in the bioaugmented treatments, although indigenous propanotrophs also biodegraded 1,4-dioxane to below 25 µg·L^-1. Nutrient additions were required to sustain biodegradation of propane and cometabolism of 1,4-dioxane. Among the unamended treatments, biodegradation of 1,4-dioxane was detected in the mid-gradient microcosms. An isolate was obtained that grows on 1,4-dioxane as a sole source of carbon and energy and identified through whole-genome sequencing as Pseudonocardia dioxivorans BERK-1. In a prior study, the same strain was isolated from an aquifer in the southeastern United States. Monod kinetic parameters for BERK-1 are similar to those for strain CB1190.

Adaption and Degradation Strategies of Methylotrophic 1,4-Dioxane Degrading Strain Xanthobacter sp. YN2 Revealed by Transcriptome-Scale Analysis

Biodegradation of 1,4-dioxane (dioxane) contamination has gained much attention for decades. In our previous work, we isolated a highly efficient dioxane degrader, Xanthobacter sp. YN2, but the underlying mechanisms of its extraordinary degradation performance remained unresolved. In this study, we performed a comparative transcriptome analysis of YN2 grown on dioxane and citrate to elucidate its genetic degradation mechanism and investigated the transcriptomes of different dioxane degradation stages (T0, T24, T48). We also analyzed the transcriptional response of YN2 over time during which the carbon source switched from citrate to dioxane. The results indicate that strain YN2 was a methylotroph, which provides YN2 a major advantage as a pollutant degrader. A large number of genes involved in dioxane metabolism were constitutively expressed prior to dioxane exposure. Multiple genes related to the catabolism of each intermediate were upregulated by treatment in response to dioxane. Glyoxylate metabolism was essential during dioxane degradation by YN2, and the key intermediate glyoxylate was metabolized through three routes: glyoxylate carboligase pathway, malate synthase pathway, and anaplerotic ethylmalonyl-CoA pathway. Genes related to quorum sensing and transporters were significantly upregulated during the early stages of degradation (T0, T24) prior to dioxane depletion, while the expression of genes encoding two-component systems was significantly increased at late degradation stages (T48) when total organic carbon in the culture was exhausted. This study is the first to report the participation of genes encoding glyoxalase, as well as methylotrophic genes xoxF and mox, in dioxane metabolism. The present study reveals multiple genetic and transcriptional strategies used by YN2 to rapidly increase biomass during growth on dioxane, achieve high degradation efficiency and tolerance, and adapt to dioxane exposure quickly, which provides useful information regarding the molecular basis for efficient dioxane biodegradation.

Cometabolic degradation of 1,4-dioxane by a tetrahydrofuran-growing Arthrobacter sp. WN18

1,4-Dioxane (dioxane), an emerging groundwater contaminant, is frequently detected in landfill leachates with its structural analog, tetrahydrofuran (THF). Along with undesirable leakage of landfill leachates, dioxane and THF inevitably percolate into groundwater leading to a broader region of contamination. Cometabolic bioremediation is an effective approach to manage commingled THF and dioxane pollution. In this study, a newly isolated bacterium Arthrobacter sp. WN18 is able to co-oxidize dioxane with THF as the primary substrate. Meanwhile, the THF-induced thmADBC gene cluster was responsible for the dioxane degradation rate indicating THF monooxygenase is the essential enzyme that initializing α-hydroxylation of THF and dioxane. Further, γ-butyrolactone and HEAA were characterized as the key metabolites of THF and dioxane, respectively. In addition, WN18 can tolerate the inhibition of trichloroethylene (5.0 mg/L) as a representative of co-existing leachate constituent, and sustain its activity at various pH (5-11), temperatures (15-42 °C), and salinities (up to 4%, as NaCl wt). Like other Arthrobacter species, WN18 also exhibited the capability of fixing nitrogen. All this evidence indicates the feasibility and advantage of WN18 as a thmADBC-catalyzed inoculator to bioremediate co-contamination of THF and dioxane.

Kinetic characterization of purified laccase from Trametes hirsuta: a study on laccase catalyzed biotransformation of 1,4-dioxane

OBJECTIVE

Laccase is one of the best known biocatalysts which degrade wide varieties of complex molecules that are both non-cyclic and cyclic in structure. The study focused on enzyme kinetics of a purified laccase from Trametes hirsuta L. fungus and its application on biotransformation of a carcinogenic molecule 1,4-dioxane.

RESULTS

Laccase was purified from white-rot fungus T. hirsuta L. which showed specific activity of 978.34 U/mg after the purification fold of 54.08. The stable laccase activity (up to 16 h) is shown at 4-6 pH and 20-40 °C temperature range. The purified enzyme exhibited significant stability for 10 metal ions up to 10 mM concentration, except for Fe²⁺ and Hg²⁺. The Cu²⁺ ion induced laccase activity up to 142% higher than the control at 10 mM concentration. The laccase enzyme kinetic parameters K_m was 20 ± 5 µM and 400 ± 60 µM, whereas K_cat was 198.29 ± 0.18/s and 80.20 ± 1.59/s for 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and guaiacol respectively. The cyclic ether 1,4-dioxane (100 ppm) was completely degraded in presence of purified laccase within 2 h of incubation and it was confirmed by HPLC and GC analysis. The oxidation reaction was accelerated by 25, 22, 6 and 19% in presence of 1 mM syringaldehyde, vanillin, ABTS and guaiacol mediators respectively.

CONCLUSIONS

In this study, fungal laccase (a natural biocatalyst) based degradation of synthetic chemical 1,4-dioxane was reported for the first time. This method has added advantages over the multiple methods reported earlier being a natural remedy.

Impact of physiologically relevant temperatures on dermal absorption of active substances - an ex-vivo study in human skin

Skin temperature plays a certain role in the dermal absorption of substances, but the extent and mechanisms of skin temperatures-induced modulation in ranges caused by physiological thermoregulation or environmental conditions are largely unknown. The influence of dermal temperature on the absorption of the model lipophilic compound (anisole) and the model hydrophilic compounds (1,4-dioxane, ethanol) through human skin was investigated at three dermal temperatures (25, 32 and 39 °C) in an ex-vivo diffusion cell model. The substances were applied to the skin and transdermal penetration was monitored. All substances showed temperature dependent variations in their penetration behavior (3 h: 25-39 °C: 202-275% increase in cumulative, transdermally penetrated amounts). The relative differences in absorption in relation to temperature were greatest within 45 min after exposure (25-39 °C: 347-653% rise in cumulated penetration), although absolute amounts absorbed were small (45 min vs. 3 h: 4.5-14.5%). Regardless of blood circulation, skin temperature significantly influences the amount and kinetics of dermal absorption. Substance-dependent, temperature-related changes of the lipid layer order or the porous pathway may facilitate penetration. The early-stage modulation of transdermal penetration indicates transappendageal absorption, which may be relevant for short-term exposures. For both, toxicological evaluation and perfusion cell studies, it is important to consider the thermal influence on absorption or to perform the latter at a standardized temperature (32±1 °C).

Stimulatory and inhibitory effects of metals on 1,4-dioxane degradation by four different 1,4-dioxane-degrading bacteria

This study evaluates the effects of various metals on 1,4-dioxane degradation by the following four bacteria: Pseudonocardia sp. D17; Pseudonocardia sp. N23; Mycobacterium sp. D6; and Rhodococcus aetherivorans JCM 14343. Eight transition metals [Co(II), Cu(II), Fe(II), Fe(III), Mn(II), Mo(VI), Ni(II), and Zn(II)] were used as the test metals. Results revealed, for the first time, that metals had not only inhibitory but also stimulatory effects on 1,4-dioxane biodegradation. Cu(II) had the most severe inhibitory effects on 1,4-dioxane degradation by all of the test strains, with significant inhibition at concentrations as low as 0.01-0.1 mg/L. This inhibition was probably caused by cellular toxicity at higher concentrations, and by inhibition of degradative enzymes at lower concentrations. In contrast, Fe(III) enhanced 1,4-dioxane degradation by Mycobacterium sp. D6 and R. aetherivorans JCM 14343 the most, while degradation by the two Pseudonocardia strains was stimulated most notably in the presence of Mn(II), even at concentrations as low as 0.001 mg/L. Enhanced degradation is likely caused by the stimulation of soluble di-iron monooxygenases (SDIMOs) involved in the initial oxidation of 1,4-dioxane. Differences in the stimulatory effects of the tested metals were likely associated with the particular SDIMO types in the test strains.

Aerobic cometabolism of 1,4-dioxane by isobutane-utilizing microorganisms including Rhodococcus rhodochrous strain 21198 in aquifer microcosms: Experimental and modeling study

Aerobic cometabolism of the emerging contaminant 1,4-dioxane (1,4-D) by isobutane-utilizing microorganisms was assessed in pure culture and aquifer microcosm studies. The bacterium Rhodococcus rhodochrous strain ATCC 21198 transformed low, environmentally-relevant concentrations of 1,4-D when grown on isobutane. Microcosms were constructed with aquifer solids from Fort Carson, Colorado, a site contaminated with 1,4-D and trichloroethene (TCE). Multiple additions of isobutane and 1,4-D over 300 days were transformed in microcosms biostimulated with isobutane and microcosms bioaugmented with strain 21198. Results showed that, over time and with sufficient inorganic nutrients, biostimulation of native microorganisms with isobutane was just as effective as bioaugmentation with strain 21198 to achieve 1,4-D transformation in the microcosms. The presence of TCE at 0.2 mg/L did not inhibit 1,4-D transformation, though TCE itself was not readily transformed. An iterative process was used to determine kinetic parameter values to fit Michaelis-Menten/Monod models to experimental data for simultaneous isobutane utilization, biomass growth, and cometabolic transformation of 1,4-D. Parameter optimization resulted in good model fit to the data over multiple transformations of isobutane and 1,4-D in both short- and long-term experiments. Results suggest low concentrations of 1,4-D studied in the microcosms were cometabolically transformed according to a pseudo first-order rate of 0.37 L/mg TSS/day of 21198. Isobutane consumption was modeled with a maximum rate of 2.58 mg/mg TSS/day and a half saturation constant of 0.09 mg/L. 1,4-D transformation was competitively inhibited by the presence of isobutane and transformation rates were significantly reduced when inorganic nutrients were limiting. Simulations of the repeated additions found a first-order microbial endogenous decay coefficient of 0.03 day^-1 fit the alternating periods of active transformation and stagnation between isobutane and 1,4-D additions over approximately one year. The model fitting process highlighted the importance of determining kinetic parameters from data representing low concentrations typically found in the environment.

Isoamericanoic Acid B from Acer tegmentosum as a Potential Phytoestrogen

Phytoestrogens derived from plants have attracted the attention of the general public and the medical community due to their potentially beneficial role in relieving menopausal symptoms. The deciduous tree Acer tegmentosum Maxim (Aceraceae) has long been utilized in Korean folk medicine to alleviate many physiological disorders, including abscesses, surgical bleeding, and liver diseases. In order to explore structurally and/or biologically new constituents from Korean medicinal plants, a comprehensive phytochemical study was carried out on the bark of A. tegmentosum. One new phenolic compound with a 1,4-benzodioxane scaffold, isoamericanoic acid B (1), as well as with nine known phenolic compounds (2–10), were successfully isolated from the aqueous extracts of the bark of A. tegmentosum. A detailed analysis using 1D and 2D NMR spectroscopy, electronic circular dichroism (ECD) spectral data, and LC/MS afforded the unambiguous structural determination of all isolated compounds, including the new compound 1. In addition, compounds 2, 4, 5, and 9 were isolated and identified from the bark of A. tegmentosum for the first time. All isolated compounds were tested for their estrogenic activities using an MCF-7 BUS cell proliferation assay, which revealed that compounds 1, 2, and 10 showed moderate estrogenic activity. To study the mechanism of this estrogenic effect, a docking simulation of compound 1, which showed the best estrogenic activity, was conducted with estrogen receptor (ER) -α and ER-β, which revealed that it interacts with the key residues of ER-α and ER-β. In addition, compound 1 had slightly higher affinity for ER-β than ER-α in the calculated Gibbs free energy for 1:ER-α and 1:ER-β. Thus, the present experimental evidence demonstrated that active compound 1 from A. tegmentosum could be a promising phytoestrogen for the development of natural estrogen supplements.

Aerobic biodegradation kinetics for 1,4-dioxane under metabolic and cometabolic conditions

Biodegradation of 1,4-dioxane has been studied extensively, however, there is insufficient information on the kinetic characteristics of cometabolism by propanotrophs and a lack of systematic comparisons to metabolic biodegradation. To fill in these gaps, experiments were performed with suspended growth cultures to determine 16 Monod kinetic coefficients that describe metabolic consumption of 1,4-dioxane by Pseudonocardia dioxanivorans CB1190 and cometabolism by the propanotrophic mixed culture ENV487 and the propanotroph Rhodococcus ruber ENV425. Maximum specific growth rates were highest for ENV425, followed by ENV487 and CB1190. Half saturation constants for 1,4-dioxane for the propanotrophs were one-half to one-quarter those for CB1190. Propane was preferentially degraded over 1,4-dioxane, but the reverse did not occur. A kinetic model was used to simulate batch biodegradation of 1,4-dioxane. Propanotrophs decreased 1,4-dioxane from 1000 to 1 μg/L in less time than CB1190 when the initial biomass concentration was 0.74 mg COD/L; metabolic biodegradation was favored at higher initial biomass concentrations and higher initial 1,4-dioxane concentrations. 1,4-Dioxane biodegradation was inhibited when oxygen was below 1.5 mg/L. The kinetic model provides a framework for comparing in situ biodegradation of 1,4-dioxane via bioaugmentation with cultures that use the contaminant as a growth substrate to those that achieve biodegradation via cometabolism.

Mechanism of 1,4-dioxane microbial degradation revealed by 16S rRNA and metatranscriptomic analyses

1,4-Dioxane (dioxane), a probable human carcinogen, often exists in industrial wastewater and domestic sewage. In this study, we applied 16S rRNA and metatranscriptomic methods to analyze the dioxane biodegradation mechanism by activated sludge. Tetrahydrofuran (THF) was added as an essential co-metabolite to promote the degradation of dioxane. We found the dioxane removal ratio increased with increasing THF concentrations. When the THF concentration increased from 60.0 to 200.0 mg/L, the dioxane degradation rate was stable. Three additions of ∼60.0 mg/L THF resulted in better dioxane degradation than one addition of 200 mg/L THF. Ammonia-oxidizing and denitrifying bacteria with methane monooxygenases (MOs) and ammonia MOs played the most important roles during the degradation of dioxane. Kyoto Encyclopedia of Genes and Genomes metabolic pathway and functional genes analyses showed that the activated sludge system was complex and stable when dioxane was added. In future studies, primers should be designed to identify specific bacteria and functional MO genes, which would help reveal the function of various bacteria and their MOs during dioxane degradation.

Synthesis and Biodegradation of Poly(l-lactide-co-β-propiolactone)

Although the copolymerizations of l-lactide (LA) with seven- or six-membered ring lactones have been extensively studied, the copolymerizations of LA with four-membered ring lactones have scarcely been reported. In this work, we studied the copolymerization of LA with β-propiolactone (PL) and the properties of the obtained copolymers. The copolymerization of LA with PL was carried out using trifluoromethanesulfonic acid as a catalyst and methanol as an initiator to produce poly(LA-co-PL) with Mn of ~50,000 and PL-content of 6-67 mol %. The Tg values of the copolymers were rapidly lowered with increasing PL-contents. The Tm and ΔHm of the copolymers gradually decreased with increasing PL-contents, indicating their decreased crystallinity. Biodegradation test of the copolymers in compost demonstrated their improved biodegradability in comparison with the homopolymer of LA.

Identification and characterization of 1,4-dioxane-degrading microbe separated from surface seawater by the seawater-charcoal perfusion apparatus

To determine the concentration of soluble 1,4-dioxane during biodegradation, a new method using of high-performance liquid chromatography equipped with a hydrophilic interaction chromatography column was developed. The developed method enabled easy and rapid determination of 1,4-dioxane, even in saline medium. Microbes capable of degrading 1,4-dioxane were selected from the seawater samples by the seawater-charcoal perfusion apparatus. Among 32 candidate 1,4-dioxane degraders,, strain RM-31 exhibited the strongest 1,4-dioxane degradation ability. 16S rDNA sequencing and the similarity analysis of strain RM-31 suggested that this organism was most closely related to Pseudonocardia carboxydivorans. This species is similar to Pseudonocardia dioxanivorans, which has previously been reported as a 1,4-dioxane degrader. Strain RM-31 could degrade 300 mg/L within 2 days. As culture incubation times increasing, the residual 1,4-dioxane concentration was decreasing and the total protein contents extracted from growth cells were increasing. The optimum initial pH of the broth medium and incubation temperature for 1,4-dioxane degradation were pH 6-8 and 25 °C. The biodegradation rate of 1,4-dioxane by strain RM-31 at 25 °C in broth medium with 3 % NaCl was almost 20 % faster than that without NaCl. It was probably a first bacteria from the seawater that can exert a strong degrading ability.

Pilot test of biological removal of 1,4-dioxane from a chemical factory wastewater by gel carrier entrapping Afipia sp. strain D1

A pilot-scale (120 L) bioreactor system using a gel carrier-entrapped pure bacterial strain, Afipia sp. strain D1, capable of degrading 1,4-dioxane as a sole carbon and energy source was constructed and applied to treat real industrial wastewater containing 1,4-dioxane from a chemical factory. Although the wastewater not only contained high concentrations of 1,4-dioxane but also considerable amounts of other organic compounds (73 mg-TOCL(-1) on average), the bioreactor could efficiently remove 1,4-dioxane without significant inhibitory effects. The reactor startup could be completed within approximately 1 month by increasing the 1,4-dioxane loading rate (0.09-0.47 kg-dioxanem(-3)d(-1)) in a stepwise manner. Effective 1,4-dioxane removal was stably maintained for 3 months with an influent 1,4-dioxane of 570-730 mg L(-1), giving an average effluent concentration and removal rate of 3.4 mg L(-1) and 0.46 kg-dioxanem(-3)d(-1), respectively. A 1,4-dioxane loading fluctuation between 0.14 and 0.72 kg-dioxanem(-3)d(-1) did not significantly affect its removal, and more than 99% removal efficiency was constantly maintained. The Monod model could well describe the relationship between the effluent 1,4-dioxane concentration and 1,4-dioxane removal rates of the bioreactors, showing that the half-saturation constant (Ks) was 28 mg L(-1).

Antimicrobial Metabolites from a Marine-Derived Actinomycete in Vietnam's East Sea

Two new compounds, a quinoline alkaloid (1) and a 1,4-dioxane derivative (2), were isolated from culture broth of the marine-derived actinomycete Micromonospora sp. (strain G019) by bioassay-guided fractionation. This actinomycete strain was isolated from sediment, collected at Cát Bà Peninsula, Vietnam. The taxonomic identification was achieved by analysis of 16S rRNA gene sequences. On the basis of morphological and phylogenetic evidence, strain G019 was assigned to the genus Micromonospora. The structures of 1 and 2 were established by spectroscopic data analysis, including one- and two-dimensional NMR, and MS. Compound 1 was found to have antibacterial activity against Escherichia coli (MIC: 48 µg/mL), Salmonella enterica (MIC: 96 µg/mL) and Enterococcus faecalis (MIC: 128 µg/mL), while compound 2 showed inhibitory activity against Enterococcusfaecalis (MIC: 32 µg/mL) and Candida albicans (MIC: 64 µg/mL).

Biodegradation of 1,4-dioxane: effects of enzyme inducers and trichloroethylene

1,4-Dioxane is a groundwater contaminant and probable human carcinogen. In this study, two well-studied degradative bacteria Mycobacterium vaccae JOB5 and Rhodococcus jostii RHA1 were examined for their 1,4-dioxane degradation ability in the presence and absence of its co-contaminant, trichloroethylene (TCE), under different oxygenase-expression conditions. These two strains were precultured with R2A broth (complex nutrient medium) before supplementation with propane or 1-butanol to induce the expression of different oxygenases. Both propane- and 1-butanol-induced JOB5 and RHA1 were able to degrade 1,4-dioxane, TCE, and mixtures of 1,4-dioxane/TCE. Complete degradation of 1,4-dioxane/TCE mixture was observed only in propane-induced strain JOB5. Inhibition was observed between 1,4-dioxane and TCE for all cells. Furthermore, product toxicity caused incomplete degradation of 1,4-dioxane by 1-butanol-induced JOB5. In general, the more TCE degraded, the greater extent of product toxicity cells experienced; however, susceptibility to product toxicity was found to be both strain- and inducer-dependent. The findings of this study provide fundamental basis for developing an effective in-situ remediation method for 1,4-dioxane-contaminated ground water and the first known study of 1,4-dioxane degradation by wild-type strain RHA1.

In vivo degradation of copolymers prepared from L-lactide, 1,3-trimethylene carbonate and glycolide as coronary stent materials

A series of high molecular weight polymers were prepared by ring opening polymerization of L-lactide (L-LA), 1,3-trimethylene carbonate (TMC) and glycolide using stannous octoate as catalyst. The resulting polymers were characterized by gel permeation chromatography, (1)H nuclear magnetic resonance, differential scanning calorimeter and tensile tests. All the polymers present high molecular weights. Compared with PLLA and PTLA copolymers, the terpolymers exhibit interesting properties such as improved toughness and lowered crystallinity with only slightly reduced mechanical strength. In vivo degradation was performed by subcutaneous implantation in rats to evaluate the potential of the copolymers as bioresorbable coronary stent material. The results show that all the polymers conserved to a large extent their mechanical properties during the first 90 days, except the strain at break which exhibited a strong decrease. Meanwhile, significant molecular weight decrease and weight loss are detected in the case of terpolymers. Therefore, the PTLGA terpolymers present a good potential for the development of totally bioresorbable coronary stents.

The impact of chlorinated solvent co-contaminants on the biodegradation kinetics of 1,4-dioxane

1,4-Dioxane (dioxane), a probable human carcinogen, is used as a solvent stabilizer for 1,1,1-trichloroethane (TCA) and other chlorinated solvents. Consequently, TCA and its abiotic breakdown product 1,1-dichloroethene (DCE) are common co-contaminants of dioxane in groundwater. The aerobic degradation of dioxane by microorganisms has been demonstrated in laboratory studies, but the potential effects of environmentally relevant chlorinated solvent co-contaminants on dioxane biodegradation have not yet been investigated. This work evaluated the effects of TCA and DCE on the transformation of dioxane by dioxane-metabolizing strain Pseudonocardia dioxanivorans CB1190, dioxane co-metabolizing strain Pseudonomas mendocina KR1, as well as Escherichia coli expressing the toluene monooxygenase of strain KR1. In all experiments, both TCA and DCE inhibited the degradation of dioxane at the tested concentrations. The inhibition was not competitive and was reversible for strain CB1190, which did not transform the chlorinated solvents. For both strain KR1 and toluene monooxygenase-expressing E. coli, inhibition of dioxane degradation by chlorinated solvents was competitive and irreversible, and the chlorinated solvents were degraded concurrently with dioxane. These data suggest that the strategies for biostimulation or bioaugmentation of dioxane will need to consider the presence of chlorinated solvents during site remediation.

Phytoremediation of 1,4-dioxane-containing recovered groundwater

The results of a pilot-scale phytoremediation study are reported in this paper. Small plots of trees established on a closed municipal waste landfill site were irrigated with recovered groundwater containing 1,4-dioxane (dioxane) and other volatile organic compounds (VOCs). The plots were managed to minimize the leaching of irrigation water, and leaching was quantified by the use of bromide tracer. Results indicated that the dioxane (2.5 microg/L) was effectively removed, probably via phytovolatilization, and that a full-scale phytoremediation system could be used. A system is now in place at the site in which the recovered groundwater can be treated using two different approaches. A physical treatment system (PTS) will be used during the winter months, and a 12 ha phytoremediation system (stands of coniferous trees) will be used during the growing season. The PTS removes VOCs using an air-stripper, and destroys dioxane using a photo-catalytic oxidation process. Treated water will be routed to the local sewer system. The phytoremediation system, located on the landfill, will be irrigated with effluent from the PTS air-stripper containing dioxane. Seasonal use of the phytoremediation system will reduce reliance on the photo-catalytic oxidation process that is extremely energy consumptive and expensive to operate.

The removal of 1,4-dioxane from polyester manufacturing process wastewater using an up-flow Biological Aerated Filter (UBAF) packed with tire chips

1,4-Dioxane is one of the by-products from the polyester manufacturing process, which has been carelessly discharged into water bodies and is a weak human carcinogen. In this study, a laboratory-scale, up-flow biological aerated filter (UBAF), packed with tire chips, was investigated for the treatment of 1,4-dioxane. The UBAF was fed with effluent, containing an average of 31 mg/L of 1,4-dioxane, discharged from an anaerobic treatment unit at H Co. in the Gumi Industrial Complex, South Korea. In the batch, a maximum of 99.5 % 1,4-dioxane was removed from an influent containing 25.6 mg/L. In the continuous mode, the optimal empty bed contact time (EBCT) and air to liquid flow rate (A:L) were 8.5 hours and 30:1, respectively. It was also found that the removal efficiency of 1,4-dioxane increased with increasing loading rate within the range 0.04 to 0.31 kg 1,4-dioxane/m(3)·day. However, as the COD:1,4-dioxane ratio was increased within the range 3 to 46 (mg/L COD)/(mg/L 1,4-dioxane), the removal efficiency unexpectedly decreased.

The effect of ethylene glycol on the phytovolatilization of 1,4-dioxane

Phytoremediation at contaminated sites is often complicated by the presence of more than one chemical However, the effects of common co-contaminants such as ethylene glycol on the phytoremediation of other chemicals, e.g., 1,4-dioxane, is not well understood. Field studies with DN34 poplar trees revealed a 28% decline in growth rate in response to 10 g/L ethylene glycol in the groundwater, thus indicating a significant and deleterious effect on tree viability, and likely, the plants' utility for phytoremediation. Thorough investigations using Arabidopsis thaliana, with its small size and rapid life cycle, indicated significant growth reduction at 10 g/L and complete inhibition of germination at 40 g/L ethylene glycol Ethylene glycol was almost as severe a stressor as the well characterized osmotic inhibitor, sorbitoL Watering potted trees with 10 g/L ethylene glycol reduced their growth by more than 50%, and similar results were observed in hydroponically grown poplar and willow trees. Under hydroponic conditions, 60 g/L ethylene glycol inhibited the phytovolatilization of l,4-dioxane by more than 80%, and all trees evapo-transpired 1,4-dioxane less efficiently than water. In fact, this efficiency differed between trees and the difference became more pronounced in the presence of ethylene glycol.

1,4-Dioxane biodegradation at low temperatures in Arctic groundwater samples

1,4-Dioxane biodegradation was investigated in microcosms prepared with groundwater and soil from an impacted site in Alaska. In addition to natural attenuation conditions (i.e., no amendments), the following treatments were tested: (a) biostimulation by addition of 1-butanol (a readily available auxiliary substrate) and inorganic nutrients; and (b) bioaugmentation with Pseudonocardia dioxanivorans CB1190, a well-characterized dioxane-degrading bacterium, or with Pseudonocardia antarctica DVS 5a1, a bacterium isolated from Antarctica. Biostimulation enhanced the degradation of 50 mg L(-1) dioxane by indigenous microorganisms (about 0.01 mg dioxane d(-1) mg protein(-1)) at both 4 and 14 degrees C, with a simultaneous increase in biomass. A more pronounced enhancement was observed through bioaugmentation. Microcosms with 50 mg L(-1) initial dioxane (representing source-zone contamination) and augmented with CB1190 degraded dioxane fastest (0.16 +/- 0.04 mg dioxane d(-1) mg protein(-1)) at 14 degrees C, and the degradation rate decreased dramatically at 4 degrees C (0.021 +/- 0.007 mg dioxane d(-1) mg protein(-1)). In contrast, microcosms with DVS 5a1 degraded dioxane at similar rates at 4 degrees C and 14 degrees C (0.018 +/- 0.004 and 0.015 +/- 0.006 mg dioxane d(-1) mg protein(-1), respectively). DVS 5a1 outperformed CB1190 when the initial dioxane concentration was low (500 microg L(-1), which is representative of the leading edge of plumes). This indicates differences in competitive advantages of these two strains. Natural attenuation microcosms also showed significant degradation over 6 months when the initial dioxane concentration was 500 microg L(-1). This is the first study to report the potential for dioxane bioremediation and natural attenuation of contaminated groundwater in sensitive cold-weather ecosystems such as the Arctic.

Microbial succession in response to 1,4-dioxane exposure in activated sludge reactors: effect of inoculum source and extra carbon addition

Bacterial community succession related to 1,4-dioxane exposure was investigated in two different activated sludge-inoculated reactors (municipal wastewater and dye industrial wastewater sludge), with or without additional carbon source, for 7 weeks. The denaturing gradient gel electrophoresis (DGGE) analysis revealed that microbial succession varied according to the inoculum sludge sources and the presence or absence of the extra carbon source. In the reactor inoculated with the municipal sludge, bacterial species belonging to alpha- and gamma-Proteobacteria and Nitrospira class were dominant over time. On the other hand, bacterial species showing significant homology to beta-Proteobacteria (e.g., Methylibium petroleiphilum PM1) and Actinobacteria class, who have been reported to have 1,4-dioxane degradation potential, were found in the industrial sludge-inoculated reactors. The appearance of these bacteria demonstrates that the microbial community structure of the inoculum and the presence of an extra carbon source affect the microbial succession in the system exposed to 1,4-dioxane.

Optimization of biological wastewater treatment conditions for 1,4-dioxane decomposition in polyester manufacturing processes

The solvent stabilizer 1,4-dioxane could have harmful effects on an ecosystem. The discharge limit of 1,4-dioxane in a body of water will be regulated at 5 mg/L in Republic of Korea. Thus, the currently operating activated sludge used in the manufacture of polyester should be properly treated to meet the regulations. Accordingly, the removal rate of 1,4-dioxane and its microbial properties was assessed at K, H and T corporations. The highest removal efficiencies were recorded at H. However, the concentration of 1,4-dioxane in the effluent of T exceeded the criterion. In addition, a microbial degradation test was conducted on 100 mg/L of 1,4-dioxane inoculated with the activated sludge from each of the three corporations. After 7 days, the 1,4-dioxane was completely removed with the H sludge and efficiencies were 67% in the T sludge and 52% in the K sludge. These results confirm that the biodegradability of 1,4-dioxane may vary in relation to the microbial properties. The microbial diversity of activated sludge of each company was therefore investigated by 16S rDNA cloning methods. In conclusion, the activated sludge of H is the most effective for the biodegradation of 1,4-dioxane. This fact is of significant concern for the industrial sector.

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.

Phyllostoxin and phyllostin, bioactive metabolites produced by Phyllosticta cirsii, a potential mycoherbicide for Cirsium arvense biocontrol

Phyllosticta cirsii, a fungal pathogen isolated from diseased Cirsium arvense leaves and evaluated as a biocontrol agent of this noxious perennial weed, produces different phytotoxic metabolites with potential herbicidal activity when grown in liquid cultures. Phyllostictines A-D, four novel oxazatricycloalkenones, were recently isolated from this pathogen and chemically and biologically characterized. Further purification of the same organic extract provided two other metabolites, named phyllostoxin (1) and phyllostin (2), which were characterized by spectroscopic technique (essentially NMR and MS). Phyllostoxin and phyllostin proved to be a new pentasubstituted bicyclo-octatrienyl acetic acid ester and a new pentasubstituted hexahydrobenzodioxine carboxylic acid methyl ester, respectively. When tested on punctured C. arvense leaves, phyllostoxin proved to be highly phytotoxic, causing rapid and large necrosis, whereas phyllostin had no phytotoxicity in this bioassay. This is not surprising, considering the noteworthy structural differences between the two compounds, suggesting the presence of active functional groups in phyllostoxin not present in the other metabolite. These results further support the focused approach of finding novel metabolites with herbicidal properties by looking at the culture extracts of weed fungal pathogens.

Modeling the mechanisms for uptake and translocation of dioxane in a soil-plant ecosystem with STELLA

Knowledge of mechanisms for uptake, translocation, and accumulation of soil contaminants in plants is essential to successful applications of the phytoremediation technique. Analysis and evaluation of these mechanisms would be greatly facilitated by the availability of a dynamic model that can predict soil contaminant uptake by roots, transport from roots through stems to leaves, and accumulation in plant during the transport process. In this study, a dynamic model for uptake and translocation of contaminants from a soil-plant ecosystem (UTCSP) was developed using the STELLA modeling tool. The structure of UTCSP consists of time-dependent simultaneous upward transport, accumulation, and transpiration of water and contaminants in the soil-plant-atmosphere continuum, which was driven by water potential gradients among soils, roots, stems, leaves, and atmosphere. The UTCSP model was calibrated using the experimental measurements and applied to predict phytoremediation of 1,4-dioxane from a sandy soil by a poplar tree. Simulation results showed that about 20% of 1,4-dioxane was removed from the soil by the poplar tree in 90 days. The simulations further revealed that while the mass of 1,4-dioxane in the poplar tree increased consecutively with time, the rates of water and 1,4-dioxane uptake and translocation in the roots, stems, and leaves have a typical diurnal distribution pattern: increasing during the day and decreasing during the night, resulting from daily variations of plant water potentials that were caused by leaf water transpiration. This study suggests that the UTCSP model is a useful tool for estimating phytoremediation of contaminants in the soil-plant ecosystems.

Biotransformation of 8:2 fluorotelomer alcohol in soil and by soil bacteria isolates

The microbial transformation of 8:2 fluorotelomer alcohol (FTOH) to perfluorocarboxylic acids, including the globally detected perfluorooctanoic acid (PFOA), has recently been confirmed to occur in mixed bacteria cultures, activated sludge, and soil. However, little is known to date about the microbes involved in the transformation. In the present study, the effect of three carrier solvents (ethanol, octanol, and 1,4-dioxane), which may serve as carbon sources, on the aerobic degradation rate of 8:2 FTOH and metabolite distribution was evaluated both in a clay loam soil and in two pure soil bacterial cultures. Biodegradation pathways appeared similar regardless of the solvent; however, significant differences in 8:2 FTOH degradation rates were observed: 1,4-dioxane > ethanol > octanol. In the presence of 1,4-dioxane, which is not easily biodegraded, 8:2 FTOH degradation was the fastest With octanol, which is a structural analogue of 8:2 FTOH, the transformation was inhibited, but upon depletion of octanol, 8:2 FTOH was biodegraded. In the pure culture study, two soil bacterial strains, Pseudomonas species OCY4 and OCW4, enriched from soil using octanol as a sole carbon source, also transformed 8:2 FTOH without prior exposure or acclimation to 8:2 FTOH. Increased biomass resulting from octanol metabolism did increase 8:2 FTOH transformation rates; however, 8:2 FTOH could not support bacterial growth, indicating the transformation by pure cultures was via cometabolic processes.

Identification of the intermediates of in vivo oxidation of 1 ,4-dioxane by monooxygenase-containing bacteria

1,4-dioxane is a probable human carcinogen and an emerging water contaminant. Monooxygenase-expressing bacteria have been shown to degrade dioxane via growth-supporting as well as cometabolic mechanisms. In this study, the intermediates of dioxane degradation by monooxygenase-expressing bacteria were determined by triple quadrupole-mass spectrometry and Fourier transform ion cyclotron resonance-mass spectrometry. The major intermediates were identified as 2-hydroxyethoxyacetic acid (HEAA), ethylene glycol, glycolate, and oxalate. Studies with uniformly labeled 14C dioxane showed that over 50% of the dioxane was mineralized to CO2 by CB1190, while 5% became biomass-associated after 48 h. Volatile organic acids and non-volatiles, respectively, accounted for 20 and 11% of the radiolabeled carbon. Although strains cometabolizing dioxane exhibited limited transformation capacities, nearly half of the initial dioxane was recovered as CO2. On the basis of these analytical results, we propose a pathway for dioxane oxidation by monooxygenase-expressing cells in which dioxane is first converted to 2-hydroxy-1,4-dioxane, which is spontaneously oxidized to HEAA. During a second monooxygenation step, HEAA is further hydroxylated, resulting in a mixture of dihydroxyethoxyacetic acids with a hydroxyl group at the ortho or para position. After cleavage of the second ether bond, small organic molecules such as ethylene glycol, glycolate, glyoxalate, and oxalate are progressively formed, which are then mineralized to CO2 via common cellular metabolic pathways. Bioremediation of dioxane via this pathway is not expected to cause an accumulation of toxic compounds in the environment.

Carbanilation of cereal β-glucans for molecular weight determination and conformational studies

Cereal beta-glucans can form aggregates in aqueous solution. The presence of aggregates in cereal beta-glucan solutions led to inaccurate determination of molecular weights and it was believed that intermolecular hydrogen bonding caused the aggregation. To eliminate aggregates, a carbanilation method for molecular weight determination of cereal beta-glucans was developed. Wheat beta-glucan samples were selected for investigation. The carbanilation method can prevent intermolecular hydrogen bonding by blocking hydroxyl groups with phenyl carbamate groups. The carbanilates of cereal beta-glucans were prepared by the reaction of cereal beta-glucans with phenylisocyanate catalyzed by DMSO and pyridine. To avoid degradation during the carbanilation reaction, relatively mild conditions were used, which led to incomplete substitution (DS: approximately 2). However, after the carbanilation reaction, the carbanilates dissolved completely in 1,4-dioxane solution without any detectable aggregates, which allowed accurate molecular weight determination. The degree of substitution (DS) of carbanilates was determined by both a nitrogen content method and an FT-IR method. The FT-IR method proved to be the more effective for DS estimation. Using this method, the converted molecular weights of cereal beta-glucans were in good agreement with the results measured in 0.5M NaOH solution, which previously was shown to be a good solvent for cereal beta-glucans. After the carbanilation reaction, conformational changes of carbanilates were studied by static and dynamic light scattering techniques. The fractal dimension (d(f)=2.27) and the structure sensitive parameters (rho >2) suggested a porous globular structure for partially carbanilated beta-glucans.

A Positron Emission Tomography Study to Assess Binding of Lecozotan, a Novel 5-Hydroxytryptamine-1A Silent Antagonist, to Brain 5-HT1A Receptors in Healthy Young and Elderly Subjects, and in Patients With Alzheimer's Disease

This positron emission tomography (PET) study was conducted to assess binding of lecozotan, a new potent and silent 5-hydroxytryptamine-1A (5-HT1A) antagonist being developed for the treatment of Alzheimer's disease (AD), to 5-HT1A receptors in the human brain using 11C-labeled WAY-100635. Lecozotan was administered as a single dose of 0.5, 1, or 5 mg to young subjects and 5 mg to elderly subjects and AD patients. PET measurements were performed at 3-4 time points over a 25-h period. Mean peak 5-HT1A receptor occupancy (RO) in young subjects (seen at 1 h) was 10%, 18%, and 44% for the three doses, respectively. Mean peak RO was slightly higher in elderly (63%) and AD patients (55%). An Emax pharmacokinetic/pharmacodynamic model adequately described the lecozotan plasma concentration-RO relationship. Steady-state peak RO is predicted to be approximately 70% for 5 mg q12 h (twice-daily). Results demonstrate that lecozotan binds to the human brain 5-HT1A receptors and has a maximum observed RO of 50-60% following a single dose of 5 mg in elderly subjects/AD patients.

Recent Advances in α1-Adrenoreceptor Antagonists as Pharmacological Tools and Therapeutic Agents

Native alpha(1)-adrenoreceptors (ARs) appear to exist as three different subtypes encoded by three genes, alpha(1A/1a), alpha(1B/1b), and alpha(1D/1d). Historically, the discovery of agents selective for each of the three alpha(1)-AR subtypes has been an active area of medicinal chemistry research because of the wide number of possible therapeutic applications. Initially introduced for the management of hypertension, alpha(1)-AR antagonists have, in fact, become increasingly common in the treatment of benign prostatic hyperplasia (BPH), and are effective therapeutic tools, when characterized by an appropriate uroselective profile. The majority of these derivatives display a competitive mechanism of action and belong to a variety of structural classes, but this review is focused on compounds belonging to the quinazoline, benzodioxane, arylpiperazine, and 1,4-dihydropyridine classes.

Biodegradation of ether pollutants by Pseudonocardia sp. strain ENV478

A bacterium designated Pseudonocardia sp. strain ENV478 was isolated by enrichment culturing on tetrahydrofuran (THF) and was screened to determine its ability to degrade a range of ether pollutants. After growth on THF, strain ENV478 degraded THF (63 mg/h/g total suspended solids [TSS]), 1,4-dioxane (21 mg/h/g TSS), 1,3-dioxolane (19 mg/h/g TSS), bis-2-chloroethylether (BCEE) (12 mg/h/g TSS), and methyl tert-butyl ether (MTBE) (9.1 mg/h/g TSS). Although the highest rates of 1,4-dioxane degradation occurred after growth on THF, strain ENV478 also degraded 1,4-dioxane after growth on sucrose, lactate, yeast extract, 2-propanol, and propane, indicating that there was some level of constitutive degradative activity. The BCEE degradation rates were about threefold higher after growth on propane (32 mg/h/g TSS) than after growth on THF, and MTBE degradation resulted in accumulation of tert-butyl alcohol. Degradation of 1,4-dioxane resulted in accumulation of 2-hydroxyethoxyacetic acid (2HEAA). Despite its inability to grow on 1,4-dioxane, strain ENV478 degraded this compound for > 80 days in aquifer microcosms. Our results suggest that the inability of strain ENV478 and possibly other THF-degrading bacteria to grow on 1,4-dioxane is related to their inability to efficiently metabolize the 1,4-dioxane degradation product 2HEAA but that strain ENV478 may nonetheless be useful as a biocatalyst for remediating 1,4-dioxane-contaminated aquifers.

Kinetics of 1,4-dioxane biodegradation by monooxygenase-expressing bacteria

1,4-Dioxane is a probable human carcinogen, and an important emerging water contaminant. In this study, the biodegradation of dioxane by 20 bacterial isolates was evaluated, and 13 were found to be capable of transforming dioxane. Dioxane served as a growth substrate for Pseudonocardia dioxanivorans CB1190 and Pseudonocardia benzenivorans B5, with yields of 0.09 g protein g dioxane(-1) and 0.03 g protein g dioxane(-1), respectively. Cometabolic transformation of dioxane was observed for monooxygenase-expressing strains that were induced with methane, propane, tetrahydrofuran, or toluene including Methylosinus trichosporium OB3b, Mycobacterium vaccae JOB5, Pseudonocardia K1, Pseudomonas mendocina KR1, Ralstonia pickettii PKO1, Burkholderia cepacia G4, and Rhodococcus RR1. Product toxicity resulted in incomplete dioxane degradation for many of the cometabolic reactions. Brief exposure to acetylene, a known monooxygenase inhibitor, prevented oxidation of dioxane in all cases, supporting the hypothesis that monooxygenase enzymes participated in the transformation of dioxane by these strains. Further, Escherichia coli TG1/pBS(Kan) containing recombinant plasmids derived from the toluene-2- and toluene-4-monooxygenases of G4, KR1 and PKO1 were also capable of cometabolic dioxane transformation. Dioxane oxidation rates measured at 50 mg/L ranged from 0.01 to 0.19 mg hr(-1) mg protein(-1) for the metabolic processes, 0.1-0.38 mg hr(-1) mg protein(-1) for cometabolism by the monooxygenase-induced strains, and 0.17-0.60 mg hr(-1) mg protein(-1) for the recombinant strains. Dioxane was not degraded by M. trichosporium OB3b expressing particulate methane monooxygenase, Pseudomonas putida mt-2 expressing a toluene side-chain monooxygenase, and PseudomonasJS150 and Pseudomonas putida F1 expressing toluene-2,3-dioxygenases. This is the first study to definitively show the role of monooxygenases in dioxane degradation using several independent lines of evidence and to describe the kinetics of metabolic and cometabolic dioxane degradation.

Synthesis and alpha4beta2 nicotinic affinity of unichiral 5-(2-pyrrolidinyl)oxazolidinones and 2-(2-pyrrolidinyl)benzodioxanes

The RS and SR enantiomers of 2-oxazolidinone and 1,4-benzodioxane bearing a 2-pyrrolidinyl substituent at the 5- and 2-position, respectively, were synthesized as candidate nicotinoids. One of the two benzodioxane stereoisomers reasonably fits the pharmacophore elements of (S)-nicotine and binds at alpha4beta2 nicotinic acetylcholine receptor with submicromolar affinity. Interestingly, both the synthesized pyrrolidinylbenzodioxanes exhibit analogous affinity at alpha(2) adrenergic receptor resembling the behaviour of some known alpha(2)-AR ligands recently proved to possess neuronal nicotinic affinity.

Mechanism study of N-dephenylation mediated through a N-para-hydroxy metabolite

A P450 catalyzed N-para-hydroxy metabolite was suggested to be a prerequisite for N-dephenylation occurrence. Although two mechanisms have been proposed to describe this process as a consequence of either a chemical degradation or P450 lead epoxidation of the hydroxy metabolite, direct evidence has not been demonstrated. In this study, we started with a novel technique using a dipeptide, Lys-Phe, to trap the byproduct of N-dephenylation, a quinone-like compound, forming a peptide adduct to facilitate LC/MS characterization. N-dephenylation via chemical degradation was assessed by LC/MS characterization of the resulting (Lys-Phe)(2)-quinone from 4-hydroxyphenyl-2-naphthylamine following interaction with Lys-Phe in pH 7.4 buffer. N-dephenylation mediated by P450 catalysis proposed was investigated in N-para-hydroxy benzodioxane derivative incubated with mouse liver microsomes in the presence of Lys-Phe in 50/50 H(2)(16)O/H(2)(18)O. LC/MS demonstrated that only one of two hydroxy oxygens in the byproduct was exchanged with water and the MS signal intensity of the (16)O labeled peptide adduct was equal to that of (18)O labeled. These observations suggested us that the origin of the oxygen in the byproduct was from water only, not from O(2). Therefore, it appears that N-dephenylation occurs via a stepwise process, namely the substrate is initially metabolized to a N-para-hydroxy metabolite by P450, which was readily oxidized to a quinone imine/iminium chemically or enzymatically, then hydrolyzed resulting in N-dephenylation. However, in our studies, the proposed P450 mechanism involving epoxidation of a N-para-hydroxy metabolite was disproved.

The in vivo and in vitro degradation behavior of poly(trimethylene carbonate)

The in vivo and in vitro degradation behavior of poly(trimethylene carbonate) (PTMC) polymers with number average molecular weights of 69 x 10(3), 89 x 10(3), 291 x 10(3) and 457 x 10(3)g/mol (respectively abbreviated as PTMC(69), PTMC(89), PTMC(291) and PTMC(457)) was investigated in detail. PTMC rods (3mm in diameter and 4mm in length) implanted in the femur and tibia of rabbits degraded by surface erosion. The mass loss of high molecular weight PTMC(457) specimens was 60wt% in 8 wks, whereas the mass loss of the lower molecular weight PTMC(89) specimens in the same period was 3 times lower. PTMC discs of different molecular weights immersed in lipase solutions (lipase from Thermomyces lanuginosus) degraded by surface erosion as well. The mass and thickness of high molecular weight PTMC(291) discs decreased linearly in time with an erosion rate of 6.7 microm/d. The erosion rate of the lower molecular weight PTMC(69) specimens was only 1.4mum/d. It is suggested that the more hydrophilic surface of the PTMC(69) specimens prevents the enzyme from acquiring a (hyper)active conformation. When PTMC discs were immersed in media varying in pH from 1 to 13, the non-enzymatic hydrolysis was extremely slow for both the high and low molecular weight samples. It can be concluded that enzymatic degradation plays an important role in the surface erosion of PTMC in vivo.

Removal of 1,4-dioxane from water using sonication: effect of adding oxidants on the degradation kinetics

This research investigates the effect of adding oxidants such as Fe0, Fe2+ and S2O8(2-) in the sonication of 1,4-dioxane (1,4-D). The results indicate that the degradation pattern of 1,4-D kinetically could be divided into three steps (initiation, acceleration, and stabilization), with the first two steps predominating. The initiation step agreed with zero order rate model, while the acceleration step was the pseudo-first order. In the presence of HCO3- as a radical scavenger, the degradations of 1,4-D and TOC were suppressed, indicating that OH radical is an important factor in the sonolysis, especially at the acceleration step. The overall degradation efficiency of 79.0% in the sonolysis of 1,4-D was achieved within 200 min. While Fe0, Fe2+ and S2O8(2-) were individually combined with sonication, the total degradation efficiency of 1,4-D increased 18.6%, 19.1% and 16.5% after 200 min, respectively. The addition of oxidants not only increased the rate constant in the acceleration step, but also changed the kinetic model from zero to pseudo-first order at the initiation step. The addition of oxidants such as Fe2+, Fe0 and S2O8(2-) in the sonication of 1,4-D also improved the mineralization of 1,4-D. However, the degradation efficiencies of 1,4-D and TOC were not statistically different (p = 0.709, ANOVA) with different oxidants such as Fe2+, Fe0 and S2O8(2-).

Degradation of 1,4-dioxane and cyclic ethers by an isolated fungus

By using 1,4-dioxane as the sole source of carbon, a 1,4-dioxane-degrading microorganism was isolated from soil. The fungus, termed strain A, was able to utilize 1,4-dioxane and many kinds of cyclic ethers as the sole source of carbon and was identified as Cordyceps sinensis from its 18S rRNA gene sequence. Ethylene glycol was identified as a degradation product of 1,4-dioxane by the use of deuterated 1,4-dioxane-d8 and gas chromatography-mass spectrometry analysis. A degradation pathway involving ethylene glycol, glycolic acid, and oxalic acid was proposed, followed by incorporation of the glycolic acid and/or oxalic acid via glyoxylic acid into the tricarboxylic acid cycle.

Pseudonocardia dioxanivorans sp. nov., a novel actinomycete that grows on 1,4-dioxane

An actinomycete strain (CB1190T) was previously isolated from industrial sludge contaminated with 1,4-dioxane. The cells of this culture are Gram-positive and exhibit branching aerial and vegetative mycelium. Analysis of the 16S rRNA gene sequence indicates that the strain belongs to the genus Pseudonocardia, closely related to Pseudonocardia hydrocarbonoxydans, P. sulfidoxydans and P. halophobica. Physiological and biochemical characteristics of CB1190T are different from those of other known Pseudonocardia species. The novel organism described here is distinguished by its ability to grow on 1,4-dioxane, which is a probable human carcinogen. This culture can also grow on tetrahydrofuran, gasoline aromatics and several other toxic environmental contaminants. Strain CB1190T is capable of fixing dinitrogen. The predominant fatty acids are 16 : 0 iso, 16 : 1 iso cis9 and 17 : 1 iso cis9. The major phospholipid fatty acids are 16 : 0 iso, 16 : 0 10-Me and 17 : 0 10-Me. The peptidoglycan belongs to type A1γ, meso-diaminopimelic acid. The major menaquinone is MK-8 (H4). Mycolic acids are absent. The G+C content is 74 mol%. Based on morphological, physiological, chemotaxonomic and phylogenetic evidence, it is proposed that strain CB1190T (=ATCC 55486T=DSM 44775T) be classified as the type strain of a novel species, Pseudonocardia dioxanivorans sp. nov. Further studies with this organism will provide insights into metabolic pathways, responsible enzymes, kinetics and the fate of 1,4-dioxane in the environment.

Novel substituted 4-phenyl-[1,3]dioxanes: potent and selective orexin receptor 2 (OX(2)R) antagonists

Orexins, also termed hypocretins, consist of two neuropeptide agonists (orexin A and B) interacting with two known G-protein coupled receptors (OX(1)R and OX(2)R). In addition to other biological functions, the orexin-2 receptor is thought to be an important modulator of sleep and wakefulness. Herein we describe a series of novel, selective OX(2)R antagonists consisting of substituted 4-phenyl-[1,3]dioxanes. One such antagonist is compound 9, 1-(2,4-dibromo-phenyl)-3-((4S,5S)-2,2-dimethyl-4-phenyl-[1,3]dioxan-5-yl)-urea, which is bound by the OX(2)R with a pK(i) of 8.3, has a pK(b) of 7.9, and is 600-fold selective for the OX(2)R over the OX(1)R.

Synthesis and Characterization of Biodegradable Poly(ethylene glycol)-block-poly(5-benzyloxy-trimethylene carbonate) Copolymers for Drug Delivery

Amphiphilic diblock copolymers with various block compositions were synthesized with monomethoxy-terminated poly(ethylene glycol) (MePEG) as the hydrophilic block and poly(5-benzyloxy-trimethylene carbonate) (PBTMC) as the hydrophobic block. When the copolymerization was conducted using MePEG as a macroinitiator and stannous 2-ethylhexanoate (Sn(Oct)2) as a catalyst, the molecular weight of the second block was uncontrollable, and the method only afforded a mixture of homopolymer and copolymer with a broad molecular weight distribution. By contrast, the use of the triethylaluminum-MePEG initiator yielded block copolymers with controllable molecular weight and a more narrow molecular weight distribution than the copolymers obtained using Sn(Oct)2. GPC and 1H NMR studies confirmed that the macroinitiator was consumed and the copolymer composition was as predicted. Two of the newly synthesized MePEG-b-PBTMC copolymers were evaluated in terms of properties primarily relating to their use in micellar drug delivery. MePEG-b-PBTMC micelles with a narrow monomodal size distribution were prepared using a high-pressure extrusion technique. The MePEG-b-PBTMC copolymers were also confirmed to be biodegradable and noncytotoxic.

Modulation of selective serotonin reuptake inhibitor and 5-HT1A antagonist activity in 8-aza-bicyclo[3.2.1]octane derivatives of 2,3-dihydro-1,4-benzodioxane

2,3-Dihydro-1,4-benzodioxanes with aryl 8-aza-bicyclo[3.2.1]oct-3-ene attachments 2 produce compounds with potent 5-HT-T affinity, and weak 5-HT(1A) affinity and alpha(1) affinity. This compares with 2,3-dihydro-1,4-benzodioxanes containing 8-aza-bicyclo[3.2.1] octan-3-ol attachments 4 which possess potent 5-HT(1A) affinity, moderate to good selectivity over alpha(1) and little 5-HT-T affinity. A 3-benzothiophene analogue of 4 (30) was synthesized which possesses potent 5-HT(1A) affinity and especially good selectivity over both alpha(1) and 5-HT-T.