Biodegradation of phthalic acid esters by immobilized microbial cells

Microorganisms capable of degrading di-n-butyl phthalate (DBP) were immobilized by polyvinyl alcohol (PVA) and used for DBP degradation. The characteristics of DBP degradation by immobilized and free cells were investigated. The experimental results showed that the degradation rate of immobilized cells was higher than that of free cells. The optimal pH and temperature for DBP degradation were determined to be 7.0 and 25°C, respectively. The semi-continuous degradation test demonstrated that high-frequency feeding of low concentration (50 mg/L) was more favourable than low-frequency feeding of high concentration (150 mg/L) for DBP degradation. The main intermediates of DBP degradation by immobilized cells were identified using a gas chromatography/mass spectrometry method. The results revealed the presence of monobutyl phthalate, phthalic acid, and protocatechuate. A tentative pathway for DBP degradation was proposed, which demonstrated that the metabolic mechanism of immobilized cells remained the same as that of the free cells.     

Bioremediation of oil sludge-contaminated soil

Bioremediation has become an important method for the restoration of oil-polluted environments by the use of indigenous or selected microbial flora. Several factors such as aeration, use of inorganic nutrients or fertilizers and the type of microbial species play a major role in the remediation of oil-contaminated sites. Experiments were undertaken for bioremediation of oil sludge-contaminated soil in the presence of a bacterial consortium, inorganic nutrients, compost and a bulking agent (wheat bran). Experiments were conducted in glass troughs for the 90-day period. Bulked soil showed more rapid degradation of oil compared to all other amendments. During the experimental period, wheat bran-amended soil showed 76% hydrocarbon removal compared to 66% in the case of inorganic nutrients-amended soil. A corresponding increase in the number of bacterial populations was also noticed. Addition of the bacterial consortium in different amendments significantly enhanced the removal of oil from the petroleum sludge from different treatment units.     

Degradation of polycyclic aromatic hydrocarbons by a bacterial consortium enriched from mangrove sediments

The biodegradability of a polycyclic aromatic hydrocarbons (PAHs) mixture consisted of fluorene (Fl), phenanthrene (Phe) and pyrene (Pyr) by a bacterial consortium enriched from mangrove sediments under sediment-free and sediment slurry conditions was investigated. The enriched consortium made up of three bacterial strains, namely Rhodococcus sp., Acinetobacter sp. and Pseudomonas sp., had a good PAH degradation capability with 100% degradation of Fl and Phe in sediment-free liquid medium after 4 weeks of growth. The Fl and Phe degradation percentages in sediment slurry were higher than that in liquid medium. Autochthonous microorganisms in sediments also possessed satisfactory PAH degradation capability and all three PAHs were almost completely degraded after 4 weeks of growth. Bioaugumentation (inoculation of the enriched consortium to sediments) showed a positive effect on PAH biodegradation after 1 week of growth. Complete biodegradation of pyrene took longer time than that for Fl and Phe, indicating the enriched bacterial consortium had preference to utilize low-molecular weight PAHs.     

Effect of bisphenol A with or without enzyme treatment on the proliferation and viability of MCF-7 cells

Recently, aqueous solutions polluted by BPA have been bioremediated by us using laccase immobilized on hydrophobic membranes in non-isothermal bioreactors. BPA degradation was checked using analytical methods. To assess in vitro the occurred bioremediation, the proliferation and viability indexes of MCF-7 cells incubated in the presence of aqueous solutions of BPA, or of enzyme-treated BPA solutions, have been measured as a function of the initial BPA concentration. The results demonstrated that: i) at each initial BPA concentration used, both the proliferation and viability indexes are a function of the duration of enzyme treatment; ii) proliferation and viability are uncoupled biological processes with respect to BPA enzyme treatment. Non-isothermal bioreactors are a useful tool for the bioremediation of aqueous solutions polluted by BPA, which is an example of an endocrine disruptor that belongs to the alkyl phenol family.     

Bioremediation of PAHs and VOCs: Advances in clay mineral–microbial interaction

Bioremediation is an effective strategy for cleaning up organic contaminants, such as polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs). Advanced bioremediation implies that biotic agents are more efficient in degrading the contaminants completely. Bioremediation by microbial degradation is often employed and to make this process efficient, natural and cost-effective materials can serve as supportive matrices. Clay/modified clay minerals are effective adsorbents of PAHs/VOCs, and readily available substrate and habitat for microorganisms in the natural soil and sediment. However, the mechanism underpinning clay-mediated biodegradation of organic compounds is often unclear, and this requires critical investigation. This review describes the role of clay/modified clay minerals in hydrocarbon bioremediation through interaction with microbial agents in specific scenarios. The vision is on a faster, more efficient and cost-effective bioremediation technique using clay-based products. This review also proposes future research directions in the field of clay modulated microbial degradation of hydrocarbons.     

Degradation and metabolite formation of 17beta-estradiol-3-sulphate in New Zealand pasture soils

Estrogens-sulphates such as 17beta-estradiol-3-sulphate and estrone-3-sulphate are excreted by livestock in the urine. These conjugates are precursors to the free counterparts 17beta-estradiol and estrone, which are endocrine disrupting chemicals. In this study microcosm laboratory experiments were conducted in three pasture soils from New Zealand to study the aerobic degradation and metabolite formation kinetics of 17beta-estradiol-3-sulphate at three different incubation temperatures. The degradation of 17beta-estradiol-3-sulphate followed a first-order kinetic and the temperature dependence of the rate constants was sufficiently described by the Arrhenius equation. Degradation was different between the three investigated soils and the rate constants across the soils were significantly correlated to the arylsulphatase activity at 7.5 and 15 degrees C. Estrone-3-sulphate and 17beta-estradiol were identified as primary metabolites and estrone as a secondary metabolite. Results suggest arylsulphatase activity originating from soil microbial biomass is the main driver for the degradation of 17beta-estradiol-3-sulphate.     

Degradation of volatile chlorinated aliphatic priority pollutants in groundwater

The known degradation products and degradative pathways involving selected volatile aliphatic chlorinated hydrocarbons in soil-groundwater systems are summarized. Current data indicate that the most commonly found products of microbial degradation of these compounds come from reductive dehalogenation, while nonmicrobial degradations tend to involve hydrolysis and/or oxidation. However, conclusions must be regarded as tentative, since most of the available studies have involved model systems and extrapolations, rather than direct studies of compounds in groundwater systems. Other potentially complicating factors, such as mobility and volatilization, are mentioned. Current knowledge is discussed in the context of data that would be desirable to obtain in future studies.     

Variation of the distribution coefficient (Kd) of selenium in soils under various microbial states

This study aimed to (i) evaluate whether the K(d) value of selenium is dependent upon the soil microbial activity and (ii) define the limitation of the use of the K(d) concept to describe selenium behaviour in soils when assessing the long-term radiological waste disposal risk. K(d) coefficients, as well as information on selenite speciation in the soil-solution, were derived from short- and long-term batch experiments with a calcareous silty clay soil in various microbial states. Soil microbial activity induced (i) an increase of the K(d) value from 16 l kg(-1) in sterile conditions to 130 l kg(-1) when the soil was amended with glucose and nitrate, and (ii) changes in selenium speciation both in the solution (presence of seleno-species other than free Se(IV)) and in the solid phase (Se linked to microorganisms). Although the K(d) coefficient adequately reflects the initial fractionation between soil-solid and soil-solution, it does not allow for speciation and microbial processes, which could affect reversibility, mobility and the long-term accumulation and uptake into crops.     

Are the parasiticidal avermectins resistant to dissipation in the environment? The case of eprinomectin

Eprinomectin (EPM) is a veterinary drug currently licensed in many countries for the treatment of endo- and ecto-parasites in cattle. Despite the notable evidence for its high toxicity to the terrestrial and aquatic environment ecosystems, its environmental behavior and fate are currently unknown. In the present research, the dissipation of EPM was studied in three soils and in cattle manure by using the OECD 307 guideline and the recently developed European Medicines Agency (EMA/CVMP/ERA/430327) guideline, respectively. The procedure presented by the FOrum for Co-ordination of pesticide models and their USe (FOCUS) was adopted for estimating the EPM degradation kinetics in soil and cattle manure. The EPM dissipation in soil was best described by the SFO (Simple First Order) and the HS (Hockey Stick) models, under aerobic and anaerobic conditions, respectively. The EPM dissipation in cattle manure was best described by the FOMC (First Order Multi Compartment) model. The Dissipation Time for the 50% of the initial EPM mass (DT₅₀) range was 38–53 days under aerobic and 691–1491 days under anaerobic conditions. In addition, the DT₅₀ for EPM in cattle manure was 333 days. Therefore, EPM could be characterized as moderately to highly persistent to dissipation in soil, which depends on soil type, its oxygen content (aerobic or anaerobic conditions in soil) and the microbial activity. Moreover, the EPM resists dissipation in cattle manure, resulting to a high load in soil after manure application in agricultural land (or direct defecation in grassland). Consequently, the high possibility for EPM accumulation in soil and cattle manure should be considered when assessing the environmental risk of the drug.     

Sediment toxicity tests involving immobilized microalgae (Phaeodactylum tricornutum Bohlin)

Populations of calcium-alginate immobilized marine diatom Phaeodactylum tricornutum were exposed to two sediments containing different levels of surfactant (LAS). Toxic responses were compared for free and immobilized algae. Although there is a direct relation between LAS content in sediment and inhibition, immobilized algae suffered less inhibition than free cells, over all when fluorescence is chosen as a biomarker for biomass. When cells are counted from dissolved beads, inhibition of growth is closer to the values found for free cells. Immobilization can be useful for in situ experiments but protection of cells inside the alginate beads against toxic capacity of xenobiotics must be taken into account.     

污水处理生物技术的应用

针对环保要求日益严格，而水源污染却越演越烈的现象，选择性地综述了湿地工艺、固定化藻类和活性污泥等生物技术在污水处理中的应用实例及其在净化废水、减轻水体富营养化方面的显著作用。三项生物技术的共同特点是高效快速、低耗节能、简易实用、管理方便且能耐受高负荷污水的冲击。净化污水主要通过基质的过滤吸附、微生物的分解代谢、植物根系或藻类的吸收利用等理化和生物的协同作用。确保和提高污水净化效果的关键因素是：湿地系统——水力负荷与停留时间、有机污染物负荷、根系发达的植物种类；固定化藻类——载体的传导性能和孔径、校固定藻类的细胞粒径、密度和生长状态、藻类生长的最适pH和温度条件；活性污泥技术——单位体积内好气性微生物的浓度及其与其他活性生物的比例、活性污泥的循环速度与回用、系统中的溶氧浓度和好气条件。     

Biodegradability of hydrocarbons in the refinery wastewater from moustorod oil refinery

The present investigation deals with the study of hydrocarbon degradation present in refinery wastewater by natural microbial flora in addition to that obtained using Ps. aeruginosa under laboratory conditions. Results indicated that Ps. aeruginosa may have a significant role in the degradation of hydrocarbons. After seven days, several of the compounds in the original wastewater were completely degraded and four compounds (n-paraffins) were partially degraded. Without Ps. aerruginosa, the same picture had been obtained after 23 days.     

亚热带喀斯特石漠化土地退化特征研究

喀斯特石漠化退化土地是目前西部地区经济发展、生态恢复与重建工作最为严重的问题之一。喀斯特石漠化是一种严重的土地退化,石漠化土地退化过程中存在社会经济反馈、动力反馈和生物原反馈等多层次反馈结构。由于喀斯特生态系统的独特性和脆弱性,喀斯特石漠化土地具有不同于其它生态脆弱区土地退化的特征,因而将其归纳为土地退化恢复过程的基岩差异性、退化恢复过程与土地利用方式的相关性、退化土地成因的地域差异性、石漠化土地的空间异质性与尺度相关性、恢复过程的土壤—地形决定性、土壤资源的不可再生性,石漠化土地退化的本质是喀斯特生态系统服务功能的下降和丧失,是一种功能性荒漠化。对石漠化土地的特征进行全面深入的探讨,有助于石漠化土地分类治理和生态恢复重建。     

Soil microbiocenosis as an indicator of stability of meadow communities in the environment polluted with heavy metals

The soil microbiota, a key component of natural ecosystems, is considered as a factor determining the stability of meadow communities. The diversity and abundance of the main ecologically significant groups of microorganisms in meadow soils have been studied along a gradient of long-term soil pollution with heavy metals in the Middle Urals. The results provide evidence for stability of the microbial assemblage formed in these soils. It has been found that the functional activity of certain physiological groups of microorganisms (nitrogen-fixing, denitrifying, and cellulolytic bacteria) and the respiratory activity of microbial communities are stimulated under conditions of heavy-metal soil pollution. Probable effects of the observed changes on mineralization of plant remains in meadow communities are discussed.     

Effect of sewage on biodegradability of hydrocarbons in refinery wastewater

The effect of the microbial flora of municipal sewage, with special reference to faecal coliform and faecal streptococci groups, on the hydrocarbons biodegradation of the refinery wastewater from the Moustorod Oil Refinery has been studied. The results indicate that sewage with its microbial flora seems to have a significant role in the biodegradation of hydrocarbons in refinery wastewater. In addition, the early degradation in the wastewater seeded by sewage reveals that faecal streptococci, in addition to other microbial flora, have a significant role in the biodegradation of hydrocarbons.     

Land treatment: A viable and successful method of treating petroleum industry wastes

Land treatment is an environmentally attractive alternative for the disposal of petroleum refinery wastes. Diverse populations of soil microorganisms degrade waste oil and other organic compounds through a series of complex reactions to yield carbon dioxide, water, and innocuous byproducts. Approximately one-half of the disposable volume of oily sludges are currently land treated at more than 100 sites across the United States under a variety of soil and climatic conditions. Maximization of biodegration rates requires an optimization of management practices which stimulate aerobic microbial populations in the soil. These management practices include addition of fertilizer, judicious waste application, and frequent cultivation. Off-site migration of oily waste constituents that would endanger groundwater quality has not been observed in several field and laboratory studies. The leached residuals are apparently adsorbed, assimilated, or inactivated in the upper soil horizons. A prudent management system, however, requires an individually tailored monitoring system with dual objectives for an early detection of off-site waste constituent transport and for evaluating the performance of waste biodegradation processes. A cost comparison for the disposal of oily wastes by currently available technologies indicates that land treatment is the most economical option.     

Fate of oil from two major oil spills: Role of microbial degradation in removing oil from the Amoco Cadiz and IXTOC I spills

The fate of oil was examined in intertidal sediments impacted by the Amoco Cadiz spill in Brittany, France, and in surface waters contaminated by the IXTOC I well blowout in the Bay of Campeche, Mexico. The role of microbial degradation in removing the contaminating hydrocarbons was assessed by laboratory determinations of numbers of hydrocarbon utilizing microorganisms, measurement of microbial hydrocarbon biodegradation potentials, by chemical analyses of samples incubated under controlled conditions and by examination of the evolution of the hydrocarbon mixture in field samples collected after the spill. Analyses included the use of ¹⁴C radiolabelled hydrocarbon tracers, glass capillary-gas chromatography and mass spectrometry. Numbers of hydrocarbon utilizing microorganisms were found to be elevated by several orders of magnitude in oil contaminated samples. Numbers of hydrocarbon utilizing microorganisms appear to provide a useful index of environmental hydrocarbon contamination. However, environmental constraints on microbial processes appear to be most important in determining actual rates of biodegradation rather than numbers of available hydrocarbon utilizing microorganisms. Very high rates of degradation were found in intertidal sediments impacted by the Amoco Cadiz spill. In contrast, rates of degradation in the Gulf of Mexico were found to be much lower, partly due to nutrient limitations and partly due to the formation of large masses of oil-water emulsion or mousse.     

Enhancement of arsenic mobility by indigenous bacteria from mine tailings as response to organic supply

Arsenic leaching by indigenous bacteria in abandoned Au-Ag mine tailings which contained approximately 3200 mg/kg of As was investigated after supply of various organic substrates. Sequential extraction analysis designed to determine the mode of As occurrence in the tailings revealed that most As (90%) was closely associated with the Fe fraction. When glucose was supplied as a C source, indigenous bacteria significantly enhanced the extent of As release from the tailings into solution under both aerobic and anaerobic conditions. Anaerobic indigenous bacteria leached more amount of As from the tailings than aerobes. Highly positive correlation between the extracted amounts of As and Fe implied that microbial dissolution of Fe(III)-oxides, whether it was ligand- and proton-promoted dissolution or reductive dissolution, might be dominantly responsible for the As release. Bacterial strains which were resistant to up to 100 mM As(V) was aerobically isolated from the tailings. One of the isolates appeared to reduce some aqueous As(V) to likely As(III) in a batch type experiment, which indicated that indigenous bacteria can mediate the electrochemical speciation and thus the mobility of As in the tailings. The results suggest that indigenous bacteria in As-contaminated tailings can increase As mobility from the solid media when microbially available organic substrates are supplied, and thus enhance the risk of As dispersion to nearby soil, sediment and groundwater.     

Colonized beads as inoculum for marine biodegradability assessment: Application to Linear Alkylbenzene Sulfonate

An innovative biodegradation test system was developed in order to fill the current gap for cost effective and environmentally relevant tools to assess marine biodegradability. Glass beads were colonized by a biofilm in an open flow-through system of seawater with continuous pre-exposure to Linear Alkylbenzene Sulfonate (LAS) (20 μg/L). Thereafter, such colonized beads were added as inoculum in different test systems. [¹⁴C]-LAS (5–100 μg/L) was added and primary and ultimate biodegradation were assessed. The bacterial density collected on the beads (10⁹ bact./mL beads) was ca. 3 orders of magnitude higher than the typical seawater content. The LAS mineralization lag phase duration decreased from 55 to < 1 days and the mineralization extent increased from 53 to 90% as the colonized beads volume increased from 10 to 275 mL. This is the first demonstration of marine bacteria's ability to mineralize LAS. On the opposite, less than 13% LAS was mineralized in seawater only. The colonized beads possibly enhanced the probability to encounter the full degraders' consortium in a low volume of seawater (100 mL).     

人工湿地系统去除藻毒素研究

以含水华的鱼塘水作为进水灌溉两套上行流－下行流人工湿地系统,系统内种植芦苇等水生植物。灌溉一周后收集人工湿地进出水水样,用ＨＰＬＣ法检测其藻毒素定量,结合温度、电位、溶氧等理化指标和细菌、藻类数量的变化,分析人工湿地系统对藻毒素的去除效果及影响其效果的可能因素。结果表明,人工湿地系统对藻毒素有一定的去除效果优于茭白－石菖蒲组合的湿地系统。在三种主要藻毒素ＲＲ、ＹＲ、ＬＲ中,湿地对ＹＲ的去除效果最好