Evaluation of the Influence of Multiple Environmental Factors on the Biodegradation of Dibenzofuran, Phenanthrene, and Pyrene by a Bacterial Consortium Using an Orthogonal Experimental Design

For a bioremediation process to be effective, we suggest to perform preliminary studies in laboratory to describe and characterize physicochemical and biological parameters (type and concentration of nutrients, type and number of microorganisms, temperature) of the environment concerned. We consider that these studies should be done by taking into account the simultaneous interaction between different factors. By knowing the response capacity to pollutants, it is possible to select and modify the right treatment conditions to enhance bioremediation.     

Enhanced Biodegradation of Naphthalene and Anthracene by Modified Vermiculite Mixed with Soil

Hydrophobic modified vermiculite mixed with soil was investigated in biodegradation experiments of naphthalene and anthracene. The experiments had been carried out on mixtures of soil and vermiculite at a proportion of 2%, 10%, and 15% and also in the absence of clay used for control. Biodegradation of the pollutants was followed by the decline of naphthalene and anthracene concentration, measured by CG. Compound mineralization was also proved by the evolution of CO₂. The results showed that in the mixture with a higher proportion of vermiculite biodegradation is enhanced compared to that performed in the absence of vermiculite. In general, when vermiculite proportions are increased, the rate of degradation increases, which may account for the bioavailability of compounds. Bioavailability is an important factor for the degradation of compounds with low solubility. Comparison of biodegradation rates shows that naphthalene is degraded faster than anthracene. The chemical structure could be responsible for this observation. However, although we did not identify the microorganism that was in the soil, we can conclude that vermiculite could be an alternative for the bioavailability of such compounds. Vermiculite in the modified form could also be very useful as a barrier to retain organic pollutants in accidental spills.     

Biodegradation of Diesel Oil in Soil by a Microbial Consortium

Biodegradation of diesel oil was performed using adiesel oil-degrading bacterial consortium, in bothlaboratory and pilot scale experiments. The bacterialconsortium was prepared in liquid for laboratory testsand for pilot scale experiments, it was prepared intwo steps, liquid and then in soil. The concentrationof diesel in soil treated with the bacterialconsortium was reduced to <15% of the initialconcentration, within a period of five weeks in bothlaboratory (135 to 19.32 g diesel kg (soil dryweight)^-1) and pilot scale (118 to 17.5 g dieselkg (soil dry weight)^-1) experiments, incomparison with controls (without bacterialconsortium), in which initial concentration of dieselwas reduced by only 5 and 15%, respectively. Dieselbiodegradation rate with the bacterial consortium was2.13 g diesel kg (soil dry weight)^-1 d^-1, itwas slightly enhanced by the addition ofNH₄NO₃ in the presence of bacterialconsortium 2.78 g diesel kg (soil dry weight)^-1d^-1. The enhancement of the microbial activity inhydrocarbon-contaminated soil can be achieved with thecombination of stepwise soil inoculation and nutrient additions.     

联苯菊酯降解菌的筛选、鉴定及降解特性研究

联苯菊酯是一种广谱高效杀虫剂,大规模的应用使其广泛残留在环境中,因此筛选联苯菊酯的高效降解菌具有重要意义。从扬州农药厂附近的地表土壤取样,利用富集驯化培养分离得到一株编号为S8的降解细菌,经表形特征、生理生化特性和16S rDNA序列分析其为醋酸钙不动杆菌（Acinetobacter calcoaceticus）,该菌株在pH7.0和30 ℃的条件下,对100 mg·L-1联苯菊酯的3 d降解率达56.4%,半衰期为60.7 h。其最适生长条件为：pH6.0~8.0,温度30~35 ℃,接种量5%。研究结果可为今后治理联苯菊酯残留污染提供理论参考。     

Biodegradation of a Bioemulsificant Exopolysaccharide (EPS2003) by Marine Bacteria

The aim of the study is to analyze the biodegradation capacity of a biosurfactant exopolysaccharide (EPS₂₀₀₃) by heterotrophic marine bacterial strains. During the initial screening performed in two sites located at the harbor of Messina for analyzing the response of marine bacterial population with the presence of biosurfactant EPS₂₀₀₃, ten bacterial strains capable to degrade this substance were isolated. Between the bacterial strains isolated, two representative bacterial strains, isoDES-01, clustered with Pseudoalteromonas sp. A28 (100%), and isoDES-07, closely related to Vibrio proteolyticus (98.9%), were chosen for mineralization and respirometry test, performed to evaluate biodegradability potential of EPS₂₀₀₃. Assays of bacterial growth and measure of concentration of total RNA were also performed. More than 90% of EPS₂₀₀₃ was mineralized by the isoDE01 strain for biomass formation and respiration, while EPS₂₀₀₃ mineralization by the isoDE-07 strain was less effective, reaching 60%. This approach combines the study of the microbial community with its functional aspects (i.e., mineralization and respirometry test) allowing a more precise assessment of biosurfactant degradation. These results enhance our knowledge of microbial ecology of EPS-degrading bacteria and the mechanisms by which this biodegradation occurs. This will prove helpful for predicting the environmental fate of these compounds and for developing practical EPS₂₀₀₃ bioremediation strategies from future marine hydrocarbon pollution.     

Biodegradation of gamma-hexachlorocyclohexane (lindane) and alpha-hexachlorocyclohexane in water and a soil slurry by a Pandoraea species

Isomers of 1,2,3,4,5,6-hexachlorocyclohexane (HCH) were some of the most widely used pesticides. Despite reduction in their production and use, HCH isomers present a serious environmental hazard. In this study, two bacterial isolates (LIN-1 and LIN-3) that can grow on gamma-HCH as a sole source of carbon and energy were isolated from an enrichment culture. In liquid cultures of LIN-1 and LIN-3, 25.0 and 45.5% removal of gamma-HCH, respectively, were achieved in 2 weeks. LIN-3 was identified as Pandoraea sp. by 16S rRNA gene sequence analysis (99% identity). Pandoraea sp. substantially degraded both gamma- and alpha-HCH isomers at concentrations of 10-200 mg L(-1) in liquid cultures. After 8 weeks of incubation in liquid culture, 89.9 and 93.3% of the gamma- and alpha-HCH isomers declined, respectively, at an initial concentration of 150 mg L(-1). In soil slurry cultures of Pandoraea sp., simulating a soil slurry phase bioremediation treatment, substantial decreases in the levels of the HCH isomers were observed at concentrations of 50-200 mg L(-1). After 9 weeks, 59.6 and 53.3% biodegradations of gamma- and alpha-HCH isomers, respectively, were achieved at 150 mg L(-1). Using two 23-mer oligonucloetide primers targeting the 330 bp region of the 16S rRNA gene of Pandoraea sp., an approximately 330 bp PCR product was successfully amplified from DNA templates prepared from bacterial colonies and soil slurry culture. This system provides a direct and rapid PCR-based molecular tool for tracking Pandoraea sp. strain LIN-3 in water and soils. These results have implied implications for the treatment of soils and water contaminated with HCH isomers.     

混合菌群强化去除泥浆体系中菲、芘的效果及影响因素

通过室内泥浆体系模拟试验,研究了混合微生物菌群(嗜热菌和多环芳烃特异性降解菌),在40℃条件下(两类微生物均能较快生长繁殖),对泥浆体系中代表性多环芳烃菲、芘的去除效果及其影响因素(水土比,葡萄糖、淀粉、水杨酸及其浓度)。结果表明:泥浆体系中混合微生物菌群对多环芳烃的去除效果显著(P0.01),单日菲去除率最大可达20.0%,芘达15.3%。随着反应进程的进行,菲和芘的去除率提高,去除速率则逐步降低,菲的半衰期1.8天小于芘4.9天,因此菲的去除较芘更快。试验得到该泥浆体系中混合微生物菌群去除多环芳烃最合适的水土比为2︰1,碳源为葡萄糖,浓度TOC_(葡萄糖):TOC_(PAHs)为2︰1。该研究结果可为泥浆体系中混合微生物菌群强化修复多环芳烃污染土壤的技术研发提供理论基础和技术支撑。     

PAHs污染土壤热脱附过程关键影响因素及脱附动力学研究

土壤多环芳烃(PAHs)污染已严重威胁生态环境安全和人类生命健康。通过异位热脱附试验探究了PAHs初始浓度、土壤含水率和土壤粒径对脱附效率的影响,并采用一级、二级动力学和指数衰减模型对PAHs热脱附过程进行拟合,以探究土壤中PAHs热脱附的去除机制。结果表明,在同等条件下,随着PAHs初始浓度的增加,脱附效率随之升高,且在热脱附20～40 min时提高初始浓度可明显提高PAHs的去除率。土壤含水率对于PAHs不同组分的作用具有一定的差异性,当土壤含水率为16%,萘(Nap)、菲(Phe)和蒽(Ant)达到最佳去除率,而荧蒽(Fla)和芘(Pyr)最大去除率对应的土壤含水率为13%。在相同脱附条件下,土壤粒径越小,土壤中PAHs的去除率越高。研究发现指数衰减模型对PAHs各组分的脱附过程具有更好的拟合效果。土壤中PAHs热脱附主要分为两个阶段:(1)PAHs受到土壤中水的蒸发作用从土壤颗粒表面快速蒸发;(2)PAHs的蒸发速率受到土壤孔隙内部扩散的限制,以非常缓慢的速度从土壤中脱除。     

Straw return decreases polycyclic aromatic hydrocarbon (PAH) accumulation in winter wheat and human health risk by enhancing PAH dissipation in rhizosphere soil

Straw return in situ, a common agronomic measure in China, has been widely used not only to increase crop yields and improve soil nutrients but also to remove polycyclic aromatic hydrocarbons (PAHs) from agricultural soils. Nevertheless, the safety risks of food crops (i.e., human health risk of wheat grains) grown in PAHs-contaminated agricultural soils amended with crop straw remain uncertain. A pot experiment was conducted in a PAHs-contaminated agricultural soil cultivated with winter wheat under different ratios of corn straw addition (0% (control, CK), 1%, 2.5%, and 5%, weight/weight). Results showed that corn straw addition significantly (P < 0.05) decreased PAH concentrations in rhizosphere soil, roots, straws, and grains by 48.32%–50.01%, 11.85%–42.67%, 9.78%–28.03%, and 14.16%–31.67%, respectively, compared with CK, whereas the transfer factors of PAHs from roots to straws were significantly (P < 0.05) increased. A correlation heatmap showed that PAH concentrations in roots, straws, and grains were positively (P < 0.01) correlated with those in rhizosphere soil. These indicated that corn straw decreased PAH accumulation in winter wheat due to the increase of PAH dissipation in the rhizosphere soil, although it enhanced PAH transfer in winter wheat. The incremental lifetime cancer risk (ILCR) model indicated that corn straw significantly (P < 0.05) decreased the human health risk of winter wheat grains by 29.73%–45.05%. Overall, corn straw apparently reduced PAH accumulation in winter wheat, ecological risk, and human health risk via enhancing PAH dissipation in the rhizosphere soil. These findings provide an important scientific basis and theoretical guidance for agricultural safety production.     

Just Add Water and Salt: the Optimisation of Petrogenic Hydrocarbon Biodegradation in Soils from Semi-arid Barrow Island, Western Australia

We investigated the potential of soil moisture and nutrient amendments to enhance the biodegradation of oil in the soils from an ecologically unique semi-arid island. This was achieved using a series of controlled laboratory incubations where moisture or nutrient levels were experimentally manipulated. Respired CO₂ increased sharply with moisture amendment reflecting the severe moisture limitation of these porous and semi-arid soils. The greatest levels of CO₂ respiration were generally obtained with a soil pore water saturation of 50?C70%. Biodegradation in these nutrient poor soils was also promoted by the moderate addition of a nitrogen fertiliser. Increased biodegradation was greater at the lowest amendment rate (100 mg N kg^?1 soil) than the higher levels (500 or 1,000 mg N kg^?1 soil), suggesting the higher application rates may introduce N toxicity. Addition of phosphorous alone had little effect, but a combined 500 mg N and 200 mg P kg^?1 soil amendment led to a synergistic increase in CO₂ respiration (3.0×), suggesting P can limit the biodegradation of hydrocarbons following exogenous N amendment.     

Process studies of a chernozemic pedon,Alberta (Canada)

Soil-forming processes in a Gleyed Black Chernozemic (Aquic Cryoboroll) pedon in central Alberta, Canada, were investigated. Vegetation similar to the present Boreal Transition Forest seems to have occupied the region during the Late Holocene. The influence of this forest ecosystem appears compatible with observed pedon properties, notably a well-structured, base-saturated mull A horizon. Rapid soil moisture depletion during the growing season limits the potential for leaching. Readily decomposed, calciumrich litter, particularly from understorey shrubs, and cation leaching from the forest canopy maintain a high base status and mild weathering environment. Faunal and other processes promote rapid formation of characteristic A horizon fabrics. The suitability of some current Canadian soil taxonomic concepts is discussed.     

Biodegradation kinetics of endosulfan by Fusarium ventricosum and a Pandoraea species

Endosulfan, classified as an organochlorine pesticide, is rated by the U.S. EPA as a Category 1 pesticide with extremely high acute toxicity. This study describes the biodegradation kinetics of endosulfan and the metabolic pathway utilized by Fusarium ventricosum and a Pandoraea sp. Complete disappearance of both alpha- and beta-endosulfan was observed during 12 days of incubation with F. ventricosum in flasks containing 100 mg L(-)(1) of endosulfan. The rate constants (k) for biodegradation of alpha- and beta-endosulfan by F. ventricosum using zero-order kinetics were 14.22 and 6.60 mg L(-)(1) day(-)(1), respectively. The Pandoraea sp. degraded about 95 and 100% of alpha- and beta-endosulfan, respectively, in 18 days of incubation in flasks spiked with 100 mg L(-)(1) of endosulfan. The rate constants (k) for biodegradation of alpha- and beta-endosulfan by the Pandoraea sp. were 8.19 and 3.78 mg L(-)(1) day(-)(1), respectively. Both fungal and bacterial strains formed less toxic endosulfan diol and endosulfan ether as metabolites during metabolism of endosulfan. The results of this study suggest that these novel strains may be used for the bioremediation of endosulfan-contaminated sites.     

Biodegradation of the Anionic Surfactant Linear Alkylbenzene Sulfonate (LAS) by Autochthonous Pseudomonas sp.

Anionic surfactants, the earliest and the most common surfactants in detergent and cosmetic product formulations contribute significantly to the pollution profile of the ecosystem. Linear alkylbenzene sulfonates (LAS), a major chemical constituent of detergents, forms an imperative group of anionic surfactants. Bioremediation of LAS by conventional processes such as activated sludge is ineffective due to the low kinetics of degradation by unsuitable organisms and foam production. Hence this study was focused on isolating and characterizing indigenous LAS-degrading bacteria from soil. Twenty different LAS-degrading bacteria were isolated from detergent-contaminated soil by enrichment culture technique and degradation efficiency was assessed by Methylene Blue Active Substances (MBAS) assay and by reverse-phase high-performance liquid chromatography (HPLC) analysis. The most efficient LAS-degrading isolates, L9 (81.33?±?0.7) and L12 (81.81?±?0.8), were selected and identified as Pseudomonas nitroreducens (MTCC 10463) and Pseudomonas aeruginosa (MTCC 10462). The 16S rDNA sequences of the isolates were deposited in NCBI GenBank under the accession numbers HQ 271083 (L9) and HQ 271084 (L12). The isolates were capable of degrading 0.05?g/l LAS at 25?°C and pH 7.0?C7.5. Presence of a solid support caused biofilm formation which in turn enhanced LAS degradation. The isolates tend to display diauxic growth with alternate carbon source such as dextrose. These isolates also have the capability to degrade other xenobiotics like hydrocarbons and pesticides. Since xenobiotic pollutants in nature occur as a mixture of compounds rather than single pollutants, the potential of these two indigenous LAS-degrading isolates to degrade multiple xenobiotics gains relevance.     

Biodegradation of oak (Quercus alba) wood during growth of the shiitake mushroom (Lentinula edodes): a molecular approach

The chemical transformations that occur during growth of the shiitake mushroom (Lentinula edodes) on oak (Quercus alba) were investigated to improve mushroom cultivation and utilization of the spent substrate. Oak logs were decayed by L. edodes over 8 years, during which time they were sampled at six intervals (30, 40, 66, 76, 77, and 101 months). Fresh and decayed oak samples were analyzed using solid-state (13)C NMR and pyrolysis-gas chromatography-mass spectrometry as well as off-line thermochemolysis with tetramethylammonium hydroxide. Degraded oak exhibited lower carbon contents and increased oxygen content compared to the control. Solid-state (13)C NMR analysis revealed that polysaccharides were the major component of both fresh and decayed oak but that L. edodes mediated the preferential loss of cellulose and xylans as compared to lignin, which remained in an altered form. Several trends point toward the degradation of lignin, including a decrease in the proportion of syringyl units as compared to guaiacyl units and a reduction in side-chain length. An increase in guaiacyl and syringyl acid-to-aldehyde ratios occurred with growth, which suggested that the fungus had caused oxidation of Calpha-Cbeta bonds. The overall effect of L. edodes on oak is similar to that of many white-rot fungi, which simultaneously degrade all cell wall components.     

Pollutant (Zn,PO4, NO2, PAH, γ-BHC,coprostanol) transport and its modeling in a small stream

The response of a lotic ecosystem to an instantaneous release of pollutants (Zn, PO₄, NO₂, PAH, γ-BHC, and coprostanol) which were included in a slug of treated sewage, was investigated. The impulse response concentration curve of pollutants was used to determine the dispersion coefficient. A mathematical model was obtained by solving the one dimensional mass transport equation with an exponential decay by a multistage implicit finite difference method and optimization of the decay constant.