Anaerobic degradation of non-substituted aromatic hydrocarbons

Aromatic hydrocarbons are among the most prevalent organic pollutants in the environment. Their removal from contaminated systems is of great concern because of the high toxicity effect on living organisms including humans. Aerobic degradation of aromatic hydrocarbons has been intensively studied and is well understood. However, many aromatics end up in habitats devoid of molecular oxygen. Nevertheless, anaerobic degradation using alternative electron acceptors is much less investigated. Here, we review the recent literature and very early progress in the elucidation of anaerobic degradation of non-substituted monocyclic (i.e. benzene) and polycyclic aromatic hydrocarbons (PAH such as naphthalene and phenanthrene). A focus will be on benzene and naphthalene as model compounds. This review concerns the microbes involved, the biochemistry of the initial activation and subsequent enzyme reactions involved in the pathway.     

Phytoremediation of toxic aromatic pollutants from soil

The enormous growth of industrialization, and the use of numerous aromatic compounds in dyestuffs, explosives, pesticides and pharmaceuticals has resulted in serious environmental pollution and has attracted considerable attention continuously over the last two decades. Many aromatic hydrocarbons, nitroaromatic compounds, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, diauxins and their derivatives are highly toxic, mutagenic and/or carcinogenic to natural microflora as well as to higher systems including humans. The increasing costs and limited efficiency of traditional physicochemical treatments of soil have spurred the development of new remediation technologies. Phytoremediation is emerging as an efficient treatment technology that uses plants to bioremediate pollutants from soil environments. Various modern tools and analytical devices have provided insight into the selection and optimization of remediation processes by various plant species. Sites heavily polluted with organic contaminants require hyperaccumulators, which could be developed by genetic engineering approaches. However, efficient hyperaccumulation by naturally occurring plants is also feasible and can be made practical by improving their nutritional and environmental requirements. Thus, phytoremediation of organics appears a very promising technology for the removal of contaminants from polluted soil. In this review, certain aspects of plant metabolism associated with phytoremediation of organic contaminants and their relevant phytoremediation efforts are discussed.IMTECH Communication No. 013/2002     

3D生物打印技术在微生物修复中的应用

排放到环境中的各种农药、多环芳烃、卤代芳烃等有机污染物以及阻燃剂等新兴污染物,对环境污染、农产品质量和环境安全造成了沉重负担。因此,有效去除环境中的有机污染物已成为迫在眉睫的挑战。3D生物打印技术已经在医学材料、制药等行业中发挥着重要作用。现在,越来越多的微生物被确定适合通过3D生物打印生产具有复杂结构和功能的生物材料。微生物的3D生物打印越来越受到环境微生物学家和生物技术专家的关注。本文综述了用于污染物微生物去除的不同3D生物打印技术的原理和优缺点,及用于微生物生物修复技术的可行性,并指出了可能遇到的限制和挑战。     

Identification and expression of two novel cytochrome P450 genes, belonging to CYP4 and a new CYP331 family, in the polychaete Capitella capitata sp.I

The polychaete Capitella capitata sp.I has a high capacity to metabolize polycyclic aromatic hydrocarbons (PAHs) which are among the most hazardous environmental pollutants with significant biological effects. In the present study, two novel cytochrome P450 (CYP) genes were identified in this species. One was named CYP331A1, the first member of a new family of CYP331, and the other CYP4AT1 is the first member of a new subfamily CYP4AT. Both of these genes are constitutively expressed in the worms and detectable by RT-PCR. The expression of CYP331A1 mRNA was observed to be more sensitive to PAH exposure than CYP4AT1, which indicated that CYP331A1 should play a more important role than CYP4AT1 in PAH metabolism in this species. Considering the importance of C. capitata sp.I in taking up PAH and other organic pollutants from contaminated marine sediments with the potential for subsequent food-chain transfer, our results are important for understanding the molecular basis of biotransformation and detoxification in this invertebrate, and also have evolutionary significance for understanding the diversity and history of the CYP superfamily.     

Phytoremediation of organic contaminants in soils

Soil pollution, a very important environmental problem, has been attracting considerable public attention over the last decades. Unfortunately, the enormous costs associated with the removal of pollutants from soils by means of traditional physicochemical methods have been encouraging companies to ignore the problem. Phytoremediation is an emerging technology that uses plants to clean up pollutants in the environment. As overwhelmingly positive results have become available regarding the ability of plants to degrade certain organic compounds, more and more people are getting involved in the phytoremediation of organic contaminants. Phytoremediation of organics appears a very promising technology for the removal of these contaminants from polluted sites.     

Identifying polycyclic aromatic hydrocarbon-degrading bacteria in oil-contaminated surface waters at Deepwater Horizon by cultivation, stable isotope probing and pyrosequencing

Polycyclic aromatic hydrocarbons (PAHs) are an important class of chemical pollutants that constitute a major component of total hydrocarbons in crude oils. Based on their poor water solubility, toxicity, persistence and potential to bioaccumulate, these compounds are recognized as high-priority pollutants in the environment and are of significant concern for human health. At oil-contaminated sites, PAH-degrading bacteria perform a critical role in the degradation and ultimate removal of these compounds. In April 2010, enormous quantities of PAHs entered the Gulf of Mexico from the thousands of tons of oil that were released from the ill-fated drilling rig Deepwater Horizon. In the ensuing months after the spill, intense research efforts were devoted to characterizing the microorganisms responsible for degrading the oil, particularly in deep waters where a large oil plume, enriched with aliphatic and low molecular-weight aromatic hydrocarbons, was found in the range of 1,000–1,300 m. PAHs, however, were found mainly confined to surface waters. This paper discusses efforts utilizing DNA-based stable isotope probing, cultivation-based techniques and metagenomics to characterize the bacterial guild associated with PAH degradation in oil-contaminated surface waters at Deepwater Horizon.     

丛枝菌根对有机污染土壤的修复作用及机理

丛枝菌根(AM)是丛枝菌根真菌(AMF)与植物根系相互作用的互惠共生体,能改良土壤结构,增强植物抗性.自然界中已知的AMF有170多种,分布广泛,且可与大多数植物共生.利用AM修复有机污染土壤正成为一个崭新的研究方向.本文综述了AM对多环芳烃、酞酸脂、石油和农药等一些典型有机污染物污染土壤的修复作用.AM修复有机污染土壤的机理主要包括:AMF代谢有机污染物;AM分泌酶,降解污染物;AM影响根系分泌作用,并促进根际微生物对有机污染物的降解;AMF宿主植物吸收积累污染物.AM修复研究中,高效AMF的筛选、复合菌种效应、土壤老化、AM作用下植物对有机污染物的吸收积累等几方面仍有待于深入研究.     

基于电活性微生物的芳香烃类污染物转化机制研究进展

芳香烃类化合物(aromatic hydrocarbon compounds)是一类基于苯环结构的有机物,广泛分布在自然环境中,难以自然降解、易被生物积累,且有很大的环境危害性。生物法是有机化合物转化降解的主流工艺,而电活性微生物(electroactive microorganisms, EAM)因其独特的胞外电子传递(extracellular electron transfer, EET)能力和生理代谢模式在芳香烃类化合物污染修复领域具有巨大的应用潜力。电活性微生物可以通过还原脱卤、脱硝与氧化开环过程相结合的方式,最终实现芳香烃类污染物的降解矿化。本文重点综述了电活性微生物降解芳香烃类污染物过程中主要还原/氧化反应机理,归纳了电活性微生物高效还原脱卤、脱硝的关键酶活、代谢途径及转化机理,分析了不同含氧条件下电活性微生物开环方式及降解代谢途径,并通过调控微生物胞外聚合物与添加导电材料等途径来提升电活性微生物的胞外电子传递过程,总结了电极电位、电极材料、电解液性质及温度等环境因子对芳香烃类化合物降解的影响,探讨了芳香烃类污染物的强化生物降解策略的可行性。最后,展望了电活性微生物降解技...     

Organic impurities in natural waters of the Tom’ basin

Analysis of gas chromatography-mass spectrometry and IR spectrometry shows that the composition of organic impurities in stream and water bodies of the Tom’ basin depends on natural and anthropogenic factors. The anthropogenic load is especially important, as the organic impurities originating from oil (paraffins, isoparaffins, naphthenes, aromatic hydrocarbons) are predominant; other pollutants of anthropogenic origin are also present (phthalates, carboxylic acids and their esters, phosphates). The composition of organic pollutants dumped into the river from each industrial zone has been analyzed both qualitatively and quantitatively.     

Utilization of iron sulfides for wastewater treatment: a critical review

Acid mine drainage due to weathering of iron sulfide minerals is one of the biggest global environmental issues. However, due to the unique physicochemical properties of natural and synthesized iron sulfides (i.e. pyrite, pyrrhotite, and mackinawite), they can be effectively used for wastewater treatment. These properties, such as ≡SH functional groups as Lewis bases, reducibility of surface Fe and S species, dissolved Fe²⁺ as a catalyst, and dissolved S^2? as an electron donor, are extensively reviewed in this article. The target water pollutants include toxic metals (i.e. lead, mercury, cadmium, and hexavalent chromium) and metalloid (i.e. arsenic), radionuclides (i.e. uranium and selenium), organic contaminants (i.e. chlorinated organic pollutants, benzene and polycyclic aromatic hydrocarbons), and nutrients (i.e. nitrogen and phosphorus). The dominant interaction mechanisms between iron sulfides and these contaminants, and the removal efficiencies are elucidated. This article focuses on the role of iron sulfides as functional materials for wastewater treatment. A recent development of nanostructured pyrrhotite with a high specific surface area for wastewater treatment is also highlighted.     

Hydrocarbons preserved in a ~2.7 Ga outcrop sample from the Fortescue Group,Pilbara Craton,Western Australia

The hydrocarbons preserved in an Archean rock were extracted, and their composition and distribution in consecutive slices from the outside to the inside of the rock were examined. The 2.7 Ga rock was collected from the Fortescue Group in the Pilbara region, Western Australia. The bitumen I (solvent‐extracted rock) and bitumen II (solvent‐extracted hydrochloric acid‐treated rock) fractions have different hydrocarbon compositions. Bitumen I contains only trace amounts of aliphatic hydrocarbons and virtually no aromatic hydrocarbons. In contrast, bitumen II contains abundant aliphatic and aromatic hydrocarbons. The difference seems to reflect the weathering history and preservational environment of the investigated rock. Aliphatic hydrocarbons in bitumen I are considered to be mainly from later hydrocarbon inputs, after initial deposition and burial, and are therefore not indigenous. The lack of aromatic hydrocarbons in bitumen I suggests a severe weathering environment since uplift and exposure of the rock at the Earth's surface in the Cenozoic. On the other hand, the high abundance of aromatic hydrocarbons in bitumen II suggests that bitumen II hydrocarbons have been physically isolated from removal by their encapsulation within carbonate minerals. The richness of aromatic hydrocarbons and the relative scarcity of aliphatic hydrocarbons may reflect the original compositions of organic materials biosynthesised in ancient organisms in the Archean era, or the high thermal maturity of the rock. Cyanobacterial biomarkers were observed in the surficial slices of the rock, which may indicate that endolithic cyanobacteria inhabited the surface outcrop. The distribution of aliphatic and aromatic hydrocarbons implies a high thermal maturity, which is consistent with the lack of any specific biomarkers, such as hopanes and steranes, and the prehnite–pumpellyite facies metamorphic grade.     

稳定同位素探针技术在有机污染物生物降解中的应用

稳定同位素探针技术(Stable isotope probing,SIP)是稳定同位素标记技术和各种分子生物学手段相结合的一系列技术总称。将其应用于探查污染物降解的功能微生物,实现了不经过分离培养直接把微生物的代谢功能、微生物间相互作用与微生物种群结合起来,从而克服了传统分离培养的缺陷,扩大了微生物资源的利用空间,具有广阔的发展前景。本文介绍了稳定同位素探针技术的基本原理和技术路线,对常规PLFA-SIP、DNA-SIP、RNA-SIP的特点进行了阐述和对比;综述了SIP在有机污染物——苯系物、多环芳烃、多氯联苯生物降解方面的研究进展,提出SIP应用于根际研究是今后该技术在生物降解研究中的一个发展方向。     

Removing environmental organic pollutants with bioremediation and phytoremediation

Hazardous organic pollutants represent a threat to human, animal, and environmental health. If left unmanaged, these pollutants could cause concern. Many researchers have stepped up efforts to find more sustainable and cost-effective alternatives to using hazardous chemicals and treatments to remove existing harmful pollutants. Environmental biotechnology, such as bioremediation and phytoremediation, is a promising field that utilizes natural resources including microbes and plants to eliminate toxic organic contaminants. This technology offers an attractive alternative to other conventional remediation processes because of its relatively low cost and environmentally-friendly method. This review discusses current biological technologies for the removal of organic contaminants, including chlorinated hydrocarbons, focusing on their limitation and recent efforts to correct the drawbacks.     

Some Physiological,Microbial, and Toxicological Aspects of the Removal of Phenanthrene by Hydroponic Cultures of Alfalfa (Medicago sativa L.)

Alfalfa (Medicago sativa L.) and other plants bearing an important root system have been shown to be effective in the removal of organic compounds, including polycyclic aromatic hydrocarbons (PAHs). Phenanthrene is one of the main contaminants arising from the petrochemical industry and is included in the USEPA's list of priority toxic pollutants. Hydroponic cultures of alfalfa were employed as a model system to evaluate their capability of removing phenanthrene and to study the plant-pollutant interaction without the interference of a soil matrix. The removal of phenanthrene was followed over a period of 30 days. The half-life of phenanthrene in hydroponics (initial concentration 50 mg L^-1) was reduced 2.7 times when plants were present. Growth index, chlorophyll content of leaves, and peroxidase activity of the roots of plants exposed to phenanthrene were lower than the corresponding values of nonexposed plants. Phenanthrene produced an acute negative effect on the total bacterial counts but also caused an increase in degraders/total bacteria ratio. The Ames Salmonella plate incorporation assay was employed to screen for potential genotoxic metabolites, which could be generated by metabolic activation of the parent compound. None of the samples exhibited a positive response. While lack of a positive response to this test is not a definitive evidence of the absence of genotoxic substances, these results suggest that the plant-assisted removal of phenanthrene merits further investigation.     

Drug metabolism in the newborn

The duration and intensity of drug action depend not only on the dose of the drug but also on the rates at which drugs are transformed to products that can be excreted readily by the kidney. Two general categories of drug metabolism occur in the liver: phase 1 reactions (oxidations-reductions and hydrolyses) and phase 2 reactions (synthetic conjugations). Phase 1 reactions produce functional groups that can participate in phase 2 reactions. Phase 1 reactions are almost nonexistent in the fetuses of laboratory animals; however, many appear in primates during the first trimester of gestation. Phase 2 reactions are deficient prenatally in both rodents and primates. Parturition triggers a surge of both phase 1 and phase 2 reactions. The lack of uniformity of the development of phase 1 oxidative reactions during the early neonatal period reflects the multiplicity of cytochrome P-450 hemoproteins, the terminal oxidases responsible for most hepatic oxidative biotransformations. The rate of recovery of chemically induced losses of cytochrome P-450 systems is age dependent.     

微生物降解多环芳烃的研究进展

多环芳烃(PAHs)是具有严重危害的环境污染物质。介绍PAHs的降解菌,降解机理和PAHs的生物修复方面的研究进展。土壤中PAHs的生物修复被认为是解决污染的有效方法,目前,菲的生物降解途径已经比较清楚,但对结构更为复杂的多环芳烃研究较少。文章还对消除环境中多环芳烃的相关生物技术提出展望。     

菲、芘、1,2,4-三氯苯对土壤高等植物根伸长抑制的生态毒性效应

测定了草甸棕壤条件下,菲、芘、１,２,４—三氮苯对高等植物（小麦、白菜、西红柿）根伸长抑制串以及复合污染毒性效应。结果表明,菲、芘、１,２,４—三氮苯浓度与植物根伸长抑制串呈显著线性或对数相关（ｐ＝０．０５）。３种化学品对植物根伸长抑制的强弱顺序为１,２,４—三氮苯＞菲＞芘。这与３种化学品的水中溶解度大小显著相关。小麦是３种供试植物中对有机污染物最敏感植物。菲、芘、１,２,４—三氮苯复合污染主表现为协同作用。     

Comparative proteomic analysis and characterization of benzo(a)pyrene removal by Microbacterium sp. strain M.CSW3 under denitrifying conditions

Bioprocess and Biosystems Engineering - High-molecular-weight polycyclic aromatic hydrocarbons are persistent organic pollutants with great environmental and human health risks and the associated...     

细菌Rieske非血红素铁环羟化酶在多环芳烃降解中的研究进展

多环芳烃是一种常见的持久性有机污染物,因具有致癌、致突变等毒性而被广泛关注。其微生物降解过程通常由羟化起始,随后脱氢、开环、一步步去除支链,最终进入三羧酸循环。Rieske 非血红素铁环羟化酶(Rieske-type non-heme iron aromatic ring-hydroxylating oxygenases , RHOs , 又称 aromatic ring-hydroxylating dioxygenases) 或细胞色素 P450 氧化酶负责将羟基加成到多环芳烃环上,将疏水性的多环芳烃转化为亲水性的衍生物,这一过程是多环芳烃降解转化的起始步骤,也是关键步骤和限速步骤之一。文中主要介绍 RHOs 的分布、底物特异性、底物识别机制以及研究 RHOs 与多环芳烃的一些技术和方法等,并对 RHOs 在环境修复技术中的潜在应用进行了展望。     

Rapid Discovery and Functional Characterization of Terpene Synthases from Four Endophytic Xylariaceae

Endophytic fungi are ubiquitous plant endosymbionts that establish complex and poorly understood relationships with their host organisms. Many endophytic fungi are known to produce a wide spectrum of volatile organic compounds (VOCs) with potential energy applications, which have been described as "mycodiesel". Many of these mycodiesel hydrocarbons are terpenes, a chemically diverse class of compounds produced by many plants, fungi, and bacteria. Due to their high energy densities, terpenes, such as pinene and bisabolene, are actively being investigated as potential "drop-in" biofuels for replacing diesel and aviation fuel. In this study, we rapidly discovered and characterized 26 terpene synthases (TPSs) derived from four endophytic fungi known to produce mycodiesel hydrocarbons. The TPS genes were expressed in an E. coli strain harboring a heterologous mevalonate pathway designed to enhance terpene production, and their product profiles were determined using Solid Phase Micro-Extraction (SPME) and GC-MS. Out of the 26 TPS’s profiled, 12 TPS’s were functional, with the majority of them exhibiting both monoterpene and sesquiterpene synthase activity.