Contribution of metabolites to mutagenicity during anaerobic biodegradation of fenitrothion

The contribution of fenitrothion and its microbial metabolites to the mutagenicity of a fenitrothion-containing solution was investigated during anaerobic biodegradation. Although a mixed culture of bacteria obtained from a paddy field degraded fenitrothion and reduced its concentration from 4.6 to 0.1 mg/l in 6 days, the indirect mutagenicity of the solution in Salmonella strain YG1029 increased. This increase was found to be partially due to amino-fenitrothion generated during the biodegradation. In addition, other unidentified metabolites contributed to the mutagenicity. In contrast, the indirect mutagenicity in strain YG1042, which was initially large because of fenitrothion, then decreased, and increased again. This increase in mutagenicity was also due to amino-fenitrothion and other unidentified metabolites. The mutagenicity in strains YG1029 and YG1042 decreased after day 6. The greatest contribution of amino-fenitrothion to the mutagenicity was calculated to be 73% and 61% in YG1029 and YG1042 on day 3 of incubation, respectively. That of unidentified metabolites was calculated at 49% and 61% on day 20, respectively. Therefore, because not all the toxic metabolites of a compound can be identified, it is important to evaluate the toxicity of a whole solution in a bioassay such as the Ames assay rather than deducing the toxicity of the solution from the combined toxicities of known metabolites.     

Mutagenicity of anaerobic fenitrothion metabolites after aerobic biodegradation

Previous studies have revealed that the mutagenicity of fenitrothion increases during anaerobic biodegradation, suggesting that this insecticide's mutagenicity could effectively increase after it pollutes anaerobic environments such as lake sediments. To investigate possible changes to the mutagenicity of fenitrothion under aerobic conditions after it had already been increased by anaerobic biodegradation, batch incubation cultures were maintained under aerobic conditions. The mutagenicity, which had increased during anaerobic biodegradation, decreased under aerobic conditions with aerobic or facultative bacteria, but did not disappear completely in 22 days. In contrast, it did not change under aerobic conditions without bacteria or under continued anaerobic conditions. These observations suggest that the mutagenicity of anaerobically metabolized fenitrothion would not necessarily decrease after it arrives in an aerobic environment: this would depend on the presence of suitable bacteria. Therefore, fenitrothion-derived mutagenic compounds may pollute the water environment, including our drinking water sources, after accidental pollution of aerobic waters. Although amino-fenitrothion generated during anaerobic biodegradation of fenitrothion was the principal mutagen, non-trivial contributions of other, unidentified metabolites to the mutagenicity were also observed.     

Fate of mutagenicity produced during anaerobic biodegradation of the herbicide chlornitrofen (CNP)

The mutagenicity of chlornitrofen (CNP)-containing solutions has been reported to increase during anaerobic biodegradation. In the present study, the fate of this increased mutagenicity under subsequent aerobic and anaerobic incubation conditions was investigated using two Salmonella tester strains, YG 1024 (a frameshift-detecting strain) and YG 1029 (a base-pair-substitution-detecting strain). Mutagenicity for both YG 1024 and YG 1029 strains increased during nine-day anaerobic biodegradation. During subsequent anaerobic incubation, the increased mutagenicity decreased gradually for YG 1029 but did not change significantly for YG 1024. By contrast, the increased mutagenicity decreased rapidly after the conversion to aerobic incubation for both YG 1024 and YG 1029 strains. The rapid decrease in mutagenicity during aerobic incubation was due to decreases, not only in an identified mutagenic metabolite (CNP-amino) but also in unidentified mutagenic metabolites.     

Oxidative biodegradation of dissolved organic matter during composting

Dissolved organic matter (DOM) plays an important role in the microbial degradation of compost since it represents the most active organic fraction, both biologically and chemically. The detailed evaluation of the changes in the chemical and biochemical characteristics of DOM induced by oxidative biodegradation, presented in this work highlights the mechanisms involved in the degradation of soluble organic matter during composting. In fact, the results show that during the initial stages of composting, DOM is highly degradable under aerobic conditions, particularly due to the predominance of labile, hydrophilic compounds such as carbohydrates, amino acids and proteins. As such compounds are degraded more resistant aromatic moieties accumulate in solution resulting in a reduction in the degradability of DOM with composting time. This decrease in degradability was found to be highly correlated with microbial oxygen demand, and could have important implications in the evaluation of the composting process.     

染料废水生物降解的产物分析

介绍了含酸性蒽醌蓝324染料废水在兼氧-好氧系统中的生物转化.产物分析结果表明:80.5%的母体染料大分子能在兼氧条件下降解成较为简单的中间产物,并且这些中间产物能在好氧条件下进一步矿化.对各反应器中主要的代谢产物分别进行紫外-可见、红外(FT-IR)和高效液相色-质联谱仪(HPLC-MS)检测分析后发现,母体染料经兼氧水解首先生成1-氨基-2-羟基蒽醌以及还原态的-OH基取代蒽醌隐色体,进一步水解生成3,4-二羟基苯甲酸.再经好氧处理,降解终产物中检测到了质荷比为101、102的脂肪类碳氢化合物、胺及醇等物质,未见有共轭结构存在.     

粪便中温好氧堆肥过程有机物的降解研究

为了生态厕所的推广使用、便于操作和节约能耗,多采用无加热的设施,即在自然条件下(对于小型生态厕所,接近中温条件)的好氧堆肥处理.了解中温好氧堆肥过程有机物的降解特性,对于生态厕所的推广使用和简化设计、操作等具有重要意义.采用密闭式好氧堆肥反应器,模拟中温(35℃)的堆肥温度,以新鲜锯末为空白载体,在含水率为60％以及连...     

Interaction of metabolites with R. rhodochrous during the biodegradation of di-ester plasticizers

The commonly used plasticizers di-ethylhexyl phthalate (DEHP) and di-ethylhexyl adipate (DEHA) are known to partially degrade in the presence of soil microorganisms, such as Rhodococcus rhodochrous, releasing persistent and toxic metabolites. The metabolites adipic acid and 2-ethylhexanol were both shown to inhibit growth of the degrading microbe. 2-Ethylhexanol enhanced the activity of ethanol dehydrogenase - an enzyme involved in its metabolism - but the activity of this enzyme was inhibited by adipic acid. The metabolite usually seen in the highest concentrations - 2-ethylhexanoic acid - did not exhibit any evidence of inhibition. It was shown that the high concentration of this metabolite was due to the inability of R. rhodochrous to degrade it. Comparisons with other small carboxylic acids supported the argument that the ethyl branch was the reason for the resistance of 2-ethylhexanoic acid to degradation. The hydrophobicity of the cell surface was shown to be a factor in plasticizer degradation. The primary carbon source could be either water-soluble or hydrophobic and a hydrophobic substrate led to a cell surface that attracted the plasticizer and facilitated degradation. The most hydrophobic of the plasticizers, DEHP, was particularly sensitive to this effect.     

Acclimation of anaerobic sludge degrading chlorophenols and the biodegradation kinetics during acclimation period

The acclimation of sludge from Hangzhou citrate factory and Hangzhou municipal wastewater treatment plant for degradation dechlorination of chlorophenols (CPs) compounds, and its biodegradation kinetics were studied in batch process with or without addition of sucrose. Three monochlorophenols (2-CP; 3-CP; 4-CP) and pentachlorophenol (PCP) were concurrently fed to different bioreactors. The parameters that were monitored included biogas production, biogas composition and chemical oxygen demand (COD). The results showed that acclimation with chlorophenol can increase the degradation activity of anaerobic sludge and degradation rate of chlorophenolic compounds, and reduce the lag time. Degradation dechlorination activity of the acclimated sludge strongly depended on sludge source, microorganism population and chlorophenol congener. 2-CP was more easily acclimated than 3-CP and 4-CP. Among the four tested compounds, 4-CP was the most difficult to be acclimated. The observed degradation rate with presence of sucrose was higher than that with absence of sucrose, suggesting that addition of the external carbon source can stimulate the formation of acclimated sludge which could effectively degrade chlorophenols. Kinetic equations of biodegradation of chlorophenols were also presented in this paper.     

微污染钦用水生物处理中痕量有机物生物降解研究述评

生物膜工艺可以有效去除微污染饮用水源中痕量有机污染物，第二级利用是稳态生物膜降解痕量有机物的主要机理。自然有机物可以作为初级基质支持稳态生物膜的生长，而痕量的合成有机物能作为第二级基质被生物膜降解，缓慢衰减的非稳态生物膜在一段时期内仍能保持对痕量有机物的高效降解。     

Interaction between co-solvents and algae in the residue dynamics of fenitrothion

Fresh and estuarine water algae maintained in laboratory microcosms simulating river-lake/estuary-bay systems were exposed to 14C-fenitrothion formulated with Atlox and tank mixed with Aerotex or Dowanol (11.5:1.5:1.5 w/v/v). Generally, the tank mix co-solvents determined the amount of uptake and the array of derivatives formed by the algae. Typically, exposed to an Aerotex mix the ratio of ethyl acetate extractable (NP) fraction: ethyl acetate unextractable (P) fraction was as 3.5:1.0, exposed to a Dowanol mix the ratio was as 1.5:1.0. Within any comparable time period, fresh water algae turned over more of the 14C-ring of fenitrothion than the estuarine genera. Turn-over was enhanced when Aerotex was the tank mix co-solvent.     

Photocatalytic removal of fenitrothion in pure and natural waters by photo-Fenton reaction

The photocatalytic removal kinetics of fenitrothion at a concentration of 0.5mgl(-1) in pure and natural waters were investigated in Fe(III)/H2O2/UV-Vis, Fe(III)/UV-Vis and H2O2/UV-Vis oxidation systems, with respect to decreases in fenitrothion concentrations with irradiation time using a solar simulator. Fenitrothion concentrations were determined by HPLC analysis. Furthermore, total mineralization of fenitrothion in these systems was evaluated by monitoring the decreases in DOC concentrations with solar simulator irradiation time by TOC analysis. It was shown that the degradation rate of fenitrothion was much faster in the Fe(III)/H2O2/UV-Vis system than the Fe(III)/UV-Vis and H2O2/UV-Vis systems in both pure and river waters. Consequently, the mineralization rate of fenitrothion was much faster in the Fe(III)/H2O2/UV-Vis system than in the other two systems. The high *OH generation rate measured in the Fe(III)/H2O2/UV-Vis system was the key to faster degradation of fenitrothion. Increases in the concentrations of H2O2 and Fe led to better final degradation of fenitrothion. These results suggest that the photo-Fenton reaction (Fe(III)/H2O2/UV-Vis) system is likely to be an effective method for removing fenitrothion from contaminated natural waters.     

Changes in lipids and sterols during composting

Pyrolysis-gas (Py-GC) chromatography was used to characterize organic [(diethyl ether (DEE) and chloroform (CHCl3)] extracts of raw and composted duck excreta enriched wood shavings from two finishing cycles (C1 and C2). Materials were collected on days 0, 8 and 23. C1 contained 1.7 % total N while C2 contained 0.9 % total N. Py-GC-MS (mass spectrometry) showed that the extracts contained n-alkanes (C12 to C32), alkenes (C12:1 to C33:1), n-fatty acids (C12 to C28), unsaturated fatty acids (C18:1 and C18:2), and sterols (cholestene, cholestadiene, stigmastene, stigmastadiene, stigmastatriene, cholesterol, stigmastanol, stigmastanone, stigmastadienone, 17-methyl dialkylsulfanyl decahydro-1H-cyclopenta [a] phenanthrene, 17-methyl dialkylsulfanyl dodecahydro-1H-cyclopenta [a] phenanthrene, and 17-methyl-17-dialkylsulfanyl decahydro-1H-cyclopenta [a] phenanthrene). Other components identified were prystene, squalene (precursor of cholesterol), phthalic acid, diphenylpropane, diphenylbut-2-ene and 1,3,6 triphenyl hex-4-ene. Our data showed significant changes in the lipid composition of duck excreta enriched wood shavings during composting, which appeared to be related to the total N content of the system.     

Biochemical mechanisms of resistance in Daphnia magna exposed to the insecticide fenitrothion

Resistance to fenitrothion and enzyme activities associated with the toxicity and metabolism of organophosphorus insecticides were measured in three genetically unique Daphnia magna clones collected from rice fields of Delta del Ebro (NE Spain) during the growing season and a lab sensitive clone. The studied clones showed up to sixfold differences in resistance to fenitrothion. The lack of correlation between in vitro sensitivity of acetylcholinesterase (AChE) to fenitrooxon and resistance to fenitrothion indicated that insensitivity of AChE to the most active oxon metabolite was not involved in the observed differences in resistance. Inhibition of mixed- function oxidases (MFOs) by piperonyl butoxide (PBO) increased the tolerance to fenitrothion by almost 20-fold in all clones without altering their relative ranking of resistance. Conversely, when exposed to fenitrooxon, the studied clones showed similar levels of tolerance, thus indicating that clonal differences in the conversion of fenitrothion to fenitrooxon by MFOs were involved in the observed resistance patterns. Despite that resistant clones showed over 1.5 higher activities of carboxilesterase (CbE) than sensitive ones, toxicity tests with 2-(O-cresyl)-4H-1,3,2-benzodioxaphosphorin-2 oxide, which is a specific inhibitor of these enzymes, evidenced that this system only contributed marginally to the observed clonal differences in tolerance. Glutathione-S-transferases activity (GST) varied across clones but not under exposure to fenitrothion, and was only related with tolerance levels in the field clones. In summary, our results indicate that MFO mediated differences on the bio-activation of the phosphorotionate OP pesticide to its active oxon metabolite contributed mostly in explaining the observed moderate levels of resistance, whereas the activities of CbE and GST had only a marginal role.     

微囊藻毒素生物降解的研究进展

蓝藻水华污染造成的最主要危害之一是产生和释放以微囊藻毒素(microcystins,MCs)为主的多种藻毒素,其在饮用水中的存在可以导致人类癌症,因此对人们的健康构成了严重威胁.从MCs降解微生物菌种、酶催化降解途径和降解基因3个方面,介绍了近年来国内外MCs生物降解的研究进展.     

苯胺生物降解极限的研究

介绍了有机物生物降解极限浓度的理论,推导得到了极限浓度的计算公式。以苯胺为目标有机物,利用经过驯化的活性污泥,通过测定其生物降解动力学参数值Ks、μmax、qmax、Ymax等计算得到了其生物降解极限质量浓度为0．025mg／L,并通过摇床试验对极限浓度进行了验证。研究表明,作为微生物生长的唯一碳源和能源,有机物生物降解存在极限浓度。     

Determination of naturally occurring MTBE biodegradation by analysing metabolites and biodegradation by-products

Methyl tert-butyl ether (MTBE) is one of the main additives in gasoline. Its degradation is known to be difficult in natural environments. In this study, significant MTBE degradation is demonstrated at a contaminated site in Leuna (eastern Germany). Since the extent of the plume appeared to be constant over the last 5 years, an extended study was performed to elucidate the degradation processes. Special attention was paid to the production, accumulation and degradation of metabolites and by-products. Groundwater samples from 105 monitoring wells were used to measure 20 different substances. During the degradation process, several intermediates such as tert-butyl alcohol (TBA), tert-butyl formate, formate and lactate were produced. However, the potentially carcinogenic by-product methacrylate was not detected in several hundred samples. At the Leuna site, MTBE degradation occurred under microaerobic conditions. In contrast to hydrocarbons and BTEX, there was no evidence for anaerobic MTBE degradation. Among the degradation products, TBA was found to be a useful intermediate to identify MTBE degradation, at least under microaerobic conditions. TBA accumulation was strongly correlated to MTBE degradation according to the kinetic properties of both degradation processes. Since maximum degradation rates (v(max)) and k(m) values were higher for MTBE (v(max)=2.3 mg/l/d and k(m)=3.2 mg/l) than for TBA (v(max)=1.35 mg/l/d and k(m)=0.05 mg/l), TBA significantly accumulated as an intermediate by-product. The field results were supported by bench scale model aquifer experiments.     

Concurrent nitrate and Fe(III) reduction during anaerobic biodegradation of phenols in a sandstone aquifer

The biodegradation of phenols (5, 60, 600 mg l⁻¹) under anaerobic conditions (nitrate enriched and unamended) was studied in laboratory microcosms with sandstone material and groundwater from within an anaerobic ammonium plume in an aquifer. The aqueous phase was sampled and analyzed for phenols and selected redox sensitive parameters on a regular basis. An experiment with sandstone material from specific depth intervals from a vertical profile across the ammonium plume was also conducted. The miniature microcosms used in this experiment were sacrificed for sampling for phenols and selected redox sensitive parameters at the end of the experiment. The sandstone material was characterized with respect to oxidation and reduction potential and Fe(II) and Fe(III) speciation prior to use for all microcosms and at the end of the experiments for selected microcosms.The redox conditions in the anaerobic microcosms were mixed nitrate and Fe(III) reducing. Nitrate and Fe(III) were apparently the dominant electron acceptors at high and low nitrate concentrations, respectively. When biomass growth is taken into account, nitrate and Fe(III) reduction constituted sufficient electron acceptor capacity for the mineralization of the phenols observed to be degraded even at an initial phenols concentration of 60 mg l⁻¹ (high) in an unamended microcosm, whereas nitrate reduction alone is unlikely to have provided sufficient electron acceptor capacity for the observed degradation of the phenols in the unamended microcosm.For microcosm systems, with solid aquifer materials, dissolution of organic substances from the solid material may occur. A quantitative determination of the speciation (mineral types and quantity) of electron acceptors associated with the solids, at levels relevant for degradation of specific organic compounds in aquifers, cannot always be obtained. Hence, complete mass balances of electron acceptor consumption for specific organic compounds degradation are difficult to confine. For aquifer materials with low initial Fe(II) content, Fe(II) determinations on solids and in aqueous phase samples may provide valuable information on Fe(III) reduction. However, in microcosms with natural sediments and where electron acceptors are associated with the sediments, complete mass-balances for substrates and electron acceptors are not likely to be obtained.     

A rapid,colorimetric, procedure for determination of fenitrothion

Abstract

Fenitrothion in formulations and on grains is determined colorimetrically as 4‐nitro‐3‐methylphenoxide, after hydrolysis at room temperature catalysed by alkaline peroxide. Interferences in determination of residue levels are removed by filtration of commodity extract through basic alumina or by barium chloride plus excess oxidant.     

废水中难降解性有机污染物的共代谢降解

微生物共代谢是污水中难降解性有机物生物降解的重要方式 ,关键酶的诱导、生长基质与目标污染物之间的竞争抑制、目标污染物及其降解产物对微生物的毒性反应是影响共代谢反应的关键因素。选择合适的生长基质、优化反应条件可以提高微生物共代谢在实际污水处理及地下水污染修复中的应用效果