QSAR for Predicting Biodegradation Rates of Polycyclic Aromatic Hydrocarbons in Aqueous Systems

The relationship between chemical structures and biodegradation rates （k b） of 22 polycyclic aromatic hydrocarbons （PAHs） was studied using density functional theory （DFT） and stepwise multiple linear regression analysis （SMLR） method.The equilibrium geometries and vibration frequency have been investigated at the B3LYP/6-31＋G（d,p） level by thinking Solvent effects using a selfconsistent reaction field （SCRF） based on the polarizable continuum model （PCM）.It was concluded that the biodegradation rate was closely related to its molecular structure,and there is one high correlation coefficient between the in-plane bending vibration frequency of the conjugated ring of PAHs （Freq） and k b.By means of regression analysis,the main factors affecting the biodegradation rate were obtained and the equation of quantitative structure-activity relationship （QSAR） was successfully established kb =-0.653＋0.001Freq＋0.068CQ＋0.049N1.Statistical evaluation of the developed QSAR showed that the relationships were statistically significant and the model had good predictive ability.The fact that a bending frequency is more important than the HOMO or LUMO energies in predicting k b suggests that the bending of benzene ring might play an important role in the enzymatic catalysis of the initial oxidation step.

Biodegradation of polycyclic aromatic hydrocarbons in sediments from the Daliao River watershed, China

The Daliao River, as an important water system in Northeast China, was reported to be heavily polluted by polycyclic aromatic hydrocarbons （PAHs）. Aerobic biodegradations of four selected PAHs （naphthalene, phenanthrene, fluorene and anthracene） alone or in their mixture in river sediments from the Daliao River water systems were studied in microcosm systems. Effects of additional carbon source, inorganic nitrogen and phosphorus, temperature variation on PAHs degradation were also investigated. Results showed that the degradation of phenanthrene in water alone system was faster than that in water-sediment combined system. Degradation of phenanthrene in sediment was enhanced by adding yeast extract and ammonium, but retarded by adding sodium acetate and not significantly influenced by adding phosphate. Although PAHs could also be biodegraded in sediment under low temperature （5~C）, much lower degradation rate was observed. Sediments from the three main streams of the Daliao River water system （the Hun River, the Taizi River and the Daliao River） demonstrated different degradation capacities and patterns to four PAHs. Average removal rates （15 or 19 d） of naphthalene, phenanthrene, fluorene and anthracene by sediment were in the range of 0.062-0.087, 0.005-0.066, 0.008- 0.016 and 0-0.059 mg/（L.d）, respectively. As a result, naphthalene was most easily degraded compound, anthracene was the hardest one. In multiple PAHs systems, the interactions between PAHs influenced each PAH biodegradation.

Methyl-β-cyclodextrin enhanced biodegradation of polycyclic aromatic hydrocarbons and associated microbial activity in contaminated soil

The contamination of soils by polycyclic aromatic hydrocarbons （PAHs） is a widespread environmental problem and the remediation of PAHs from these areas has been a major concern. The effectiveness of many in situ bioremediation systems may be constrained by low contaminant bioavailability due to limited aqueous solubility or a large magnitude of sorption. The objective of this research was to evaluate the effect of methyl-β-cyclodextrin （MCD） on bioaugmentation by Paracoccus sp. strain HPD-2 of an aged PAH-contaminated soil. When 10% （W/W） MCD amendment was combined with bioaugmentation by the PAH-degrading bacterium Paracoccus sp. strain HPD-2, the percentage degradation of total PAHs was significantly enhanced up to 34.8%. Higher counts of culturable PAH- degrading bacteria and higher soil dehydrogenase and soil polyphenol oxidase activities were observed in 10% （W/W） MCD-assisted bioaugmentation soil. This MCD-assisted bioaugmentation strategy showed significant increases （p 〈 0.05） in the average well color development （AWCD） obtained by the BIOLOG Eco plate assay, Shannon-Weaver index （H） and Simpson index （λ） compared with the controls, implying that this strategy at least partially restored the microbiological functioning of the PAH-contaminated soil. The results suggest that MCD-aided bioaugmentation by Paracoccus sp. strain HPD-2 may be a promising practical bioremediation strategy for aged PAH-contaminated soils.

Relationship between the Biodegradability and Structure of Polycyclic Aromatic Hydrocarbons

21 Physicochemical and quantum chemical parameters of 17 kinds of polycyclic aromatic hydrocarbons were calculated by using semi-empirical MOPAC AM1 method. By means of Partial Least Squares （PLS）, quantitative structure-biodegradation relationship （QSBR） study was performed with the logarithm of specific biodegradation rates （logKb）. The optimal model was obtained, and the result showed that the first-order molecular connectivity index （^1X）, the energy of the lowest unoccupied molecular orbital （Elumo）, logarithm of n-octyl alcohol/water partition coefficient （logP） and torsion energy （Et） are the dominant factors governing the biodegradability of polyeyelie aromatic hydrocarbons, and the effect of second-order valence molecular connectivity index （^2X^V）, the third-order valence molecular connectivity index （^3X^V） and molar refractivity （Rm） should not be ignored.

Biodegradation of polycyclic aromatic hydrocarbons(PAHs)by fungal enzymes:A review

Polycyclic aromatic hydrocarbons（PAHs） are a large group of chemicals.They represent an important concern due to their widespread distribution in the environment,their resistance to biodegradation,their potential to bioaccumulate and their harmful effects.Several pilot treatments have been implemented to prevent economic consequences and deterioration of soil and water quality.As a promising option,fungal enzymes are regarded as a powerful choice for degradation of PAHs.Phanerochaete chrysosporium,Pleurotus ostreatus and Bjerkandera adusta are most commonly used for the degradation of such compounds due to their production of ligninolytic enzymes such as lignin peroxidase,manganese peroxidase and laccase.The rate of biodegradation depends on many culture conditions,such as temperature,oxygen,accessibility of nutrients and agitated or shallow culture.Moreover,the addition of biosurfactants can strongly modify the enzyme activity.The removal of PAHs is dependent on the ionization potential.The study of the kinetics is not completely comprehended,and it becomes more challenging when fungi are applied for bioremediation.Degradation studies in soil are much more complicated than liquid cultures because of the heterogeneity of soil,thus,many factors should be considered when studying soil bioremediation,such as desorption and bioavailability of PAHs.Different degradation pathways can be suggested.The peroxidases are heme-containing enzymes having common catalytic cycles.One molecule of hydrogen peroxide oxidizes the resting enzyme withdrawing two electrons.Subsequently,the peroxidase is reduced back in two steps of one electron oxidation.Laccases are copper-containing oxidases.They reduce molecular oxygen to water and oxidize phenolic compounds.

Biosorption and biodegradation of polycyclic aromatic hydrocarbons by Phanerochaete chrysosporium in aqueous solution

Biosorption and biodegradation of phenanthrene and pyrene by live and heat-killed Phanerochaete chrysosporium are investigated to elucidate the bio-dissipation mechanisms of polycyclic aromatic hydrocarbons(PAHs) in aqueous solution and its regulating factors.The effects of nutrient conditions(carbon source and nitrogen source concentrations),the co-existing Cu 2+,and repeated-batch feed of PAHs on the biosorption and biodegradation are systematically studied.The removal of PAHs by dead bodies of P.chrysosporium is attributed to biosorption only,and the respective partition coefficients of phenanthrene and pyrene are 4040 and 17500 L/kg.Both biosorption and biodegradation contribute to the dissipation of PAHs by live P.chrysosporium in water.After a 3-d incubation,the removal percentage via biosorption are 19.71% and 52.21% for phenanthrene and pyrene,respectively.With the increase of the incubation time(3 40 d),biodegradation gradually increases from 20.40% to 60.62% for phenanthrene,and from 15.55% to 49.21% for pyrene.Correspondingly,the stored-PAHs in the fungal bodies decrease.Under the carbon-rich and nitrogen-limit nutrient conditions,the removal efficiency and biodegradation of phenanthrene and pyrene are significantly promoted,i.e.99.55% and 92.77% for phenanthrene,and 99.47% and 83.97% for pyrene after a 60-d incubation.This phenomenon is ascribed to enhanced-biosorption due to the increase of fungal biomass under carbon-rich condition,and to stimulated-biodegradation under nitrogen-limit condition.For the repeated-batch feed of phenanthrene,the pollutant is continuously removed by live P.chrysosporium,and the contribution of biodegradation is enhanced with the repeated cycles.After 3 cycles,the biodegradation percentage is up to 90% with each cycle of a 6-d incubation.

PAH-biodegradation potential of indigenous microorganisms: evidence from the respiratory activity of surfacesediments in the Quanzhou Bay in China

Seven stations were established in the Quanzhou Bay （24.73°-24.96°N, 118.50°-118.70°E） in China on three cruises to determine the concentrations of polycyclic aromatic hydrocarbons （PAHs） and the numbers of PAH-degrading bacteria in surface sediments. Assessing the biodegradation potential of indigenous microorganisms by measuring the respiratory intensity with the addition of PAHs in sediment samples was also one of the aims of this study. The results show that the total PAH concentrations of the sediments were 99.23-345.53 ng/g dry weight （d.w.）, and the PAHs composition pattern in the sediments was dominated by phenanthrene, fluoranthene and pyrene. The numbers of phenanthrene, fluoranthene and pyrene-degrading bacteria during three cruises were 1.42×10^3-8.93×10^4 CFU/g d.w., 8.29×10^3 9.43×10^4 CFU/g d.w. and 7.05×10^3-9.43×10^4 CFU/g d.w., respectively. The addition of three model PAH compounds （phenanthrene, fluoranthene and pyrene） showed a great influence on the increasing of the microbial activity in the sediments. And there was a significant correlation among the change of respiratory activity, PAH concentration and the number of PAH-degrading bacteria. The change in respiratory activity under PAHs selective pressure could, to a certain extent, indicate the potential degradative activity of the PAH-degrading microbial community.

Degradation of polycyclic aromatic hydrocarbons by Pseudomonas sp.JM2 isolated from active sewage sludge of chemical plant

It is important to screen strains that can decompose polycyclic aromatic hydrocarbons （PAHs） completely and rapidly with good adaptability for bioremedlation in a local area. A bacterial strain JM2, which uses pbenanthrene as its sole carbon source, was isolated from the active sewage sludge from a chemical plant in Jilin, China and identified as Pseudomonas based on 16S rDNA gene sequence analysis. Although the optimal growth conditions were determined to be pH 6.0 and 37~C, JM2 showed a broad pH and temperature profile. At pH 4.5 and 9.3, JM2 could degrade more than 40% of fluorene and phenanthrene （50 mg/L each） within 4 days. In addition, when the temperature was as low as 4~C, JM2 could degrade up to 24% fluorene and 12% phenanthrene. This showed the potential for JM2 to be applied in bioremediation over winter or in cold regions. Moreover, a nutrient augmentation study showed that adding formate into media could promote PAH degradation, while the supplement of salicylate had an inhibitive effect. Furthermore, in a metabolic pathway study, salicylate, phthalic acid, and 9-fluorenone were detected during the degradation of fluorene or phenanthrene. In conclusion, Pseudomonas sp. JM2 is a high performance strain in the degradation of fluorene and phenanthrene under extreme pH and temperature conditions. It might be useful in the bioremediation of PAHs.

Role of nutrients in the utilization of polycyclic aromatic hydrocarbons by halotolerant bacterial strain

A halotolerant bacterial strain VA1 isolated from marine environment was studied for its ability to utilize polycylic aromatic hydrocarbons （PAHs） under saline condition. Anthracene and pyrene were used as representatives for the utilization of PAH by the bacterial strain. Glucose and sodium citrate were used as additional carbon sources to enhance the PAH utilization. The strain VA1 was able to utilize anthracene （73%） and pyrene （66%） without any additional substrate. In the presence of additional carbon sources （glucose]sodium citrate） the utilization of PAH was faster. PAH was utilized faster by VA 1 in the presence of glucose than sodium citrate. The stain utilized 87% and 83% of anthracene and pyrene with glucose as carbon source and with sodium citrate the strain utilized 81% and 76% respectively in 4 days. Urea as an alternative source of nitrogen also enhanced the utilization of PAHs （anthracene and pyrene） by the bacterial strain up to 88% and 84% in 4 days. Sodium nitrate as nitrogen source was not able to enhance the PAH utilization rate. Phenotypic and phlyogenetic analysis proved that the PAHs utilizing halotolerant strain VA1 belongs to Ochrobactrum sp.

Impact of solids on biphasic biodegradation of phenanthrene in the presence of hydroxypropyl-β-cyclodextrin(HPCD)

The consequence of polycyclic aromatic hydrocarbons(PAHs)in the environment is of great concern.The hydrophobic properties of PAHs significantly impact phase distribution causing limited bioavailability.Enhanced biodegradation has been extensively carried out by surfactants and the redeployment effect was recognized.However,the quantitative relationship concerning the impact of solids was rarely reported.A batch of biphasic tests were carried out by introducing Mycobacterium vanbaalenii PYR-1 and hydroxypropyl-β-cyclodextrin(HPCD)into a mixture of phenanthrene solution and various glass beads(GB37-63,GB105-125,and GB350-500).The comparative results demonstrated that HPCD had little effect on microbial growth and was not degradable by bacterium.A model was proposed to describe the biodegradation process.The regression results indicated that the partition coefficient kd(1.234,0.726 and 0.448 L·g–1)and the degradation rate k(0 mmol·L^(–1):0.055,0.094,and 0.112;20 mmol·L^(–1):0.126,0.141,and 0.156;40 mmol·L^(–1):0.141,0.156 and 0.184 d^(–1))were positively and negatively correlated with the calculated total surface area(TSA)of solids,respectively.Degradation enhanced in the presence of HPCD,and the enhancing factor f was calculated(20 mmol·L^(–1):15.16,40.01,and 145.5;40 mmol·L^(–1):13.29,37.97,and 138.4),indicating that the impact of solids was significant for the enhancement of biodegradation.

Anaerobic biodegradation of PAHs in mangrove sediment with amendment of NaHCO_3

Mangrove sediment is unique in chemical and biological properties. Many of them suffer polycyclic aromatic hydrocarbon（PAH） contamination. However, the study on PAH biological remediation for mangrove sediment is deficient. Enriched PAH-degrading microbial consortium and electron acceptor amendment are considered as two effective measures. Compared to other electron acceptors, the study on CO2, which is used by methanogens, is still seldom. This study investigated the effect of Na HCO3 amendment on the anaerobic biodegradation of four mixed PAHs, namely fluorene（Fl）, phenanthrene（Phe）,fluoranthene（Flua） and pyrene（Pyr）, with or without enriched PAH-degrading microbial consortium in mangrove sediment slurry. The trends of various parameters, including PAH concentrations, microbial population size, electron-transport system activities, electron acceptor and anaerobic gas production were monitored. The results revealed that the inoculation of enriched PAH-degrading consortium had a significant effect with half lives shortened by 7–13 days for 3-ring PAHs and 11–24 days for 4-ring PAHs. While Na HCO3 amendment did not have a significant effect on the biodegradation of PAHs and other parameters, except that CO2 gas in the headspace of experimental flasks was increased.One of the possible reasons is that mangrove sediment contains high concentrations of other electron acceptors which are easier to be utilized by anaerobic bacteria, the other one is that the anaerobes in mangrove sediment can produce enough CO2 gas even without adding Na HCO3.

Impact of Anthracene Addition on Microbial Community Structure in Soil Microcosms from Contaminated and Uncontaminated Sites

Objective This paper aims to investigate the impact of anthracene addition on microbial community in agricultural soil irrigated with tap water or reclaimed wastewater.Methods The changes of microbial community were characterized by terminal restriction fragment length polymorphism in combination with 16S rRNA gene clone library analysis.Results A significant change in microbial community composition was observed during the biodegradation of anthracene,with dominantly enriched members from the genus Methylophilus.Conclusion This work might be useful for developing techniques for the isolation of novel putative PAH degrader.

黄河三角洲沉积物烃类污染及来源

黄河三角洲沉积物中游离(气态和液体)烃含量为0.01~0.14 mg/g.它们富集在黏土粒级之中.沉积物中石油成因的烃类主要来自三角洲地区,热解成因的烃类主要来自黄河流域.黄河流域工业和民用煤不完全燃烧时所产生的多环芳烃应是黄河三角洲沉积物中热解成因烃类的重要来源.在遭受原油污染地区,原油可快速地被微生物降解.

鞘氨醇单胞菌研究进展

鞘氨醇单胞菌属(Sphingomonas)是1990年才重新划分的一个新属,由于其特有的生态分布与代谢特征,已引起了环境微生物学者的重视.本文综述了鞘氨醇单胞菌的细胞结构与功能,以及生态分布与代谢特征方面的研究进展.鞘氨醇单胞菌具有特殊的细胞结构,最显著的是细胞膜用鞘脂糖代替了脂多糖,这使其与传统意义上的革兰氏阴性菌具有显著区别.鞘氨醇单胞菌耐受贫营养的代谢机制使其在自然界中有着极强的生命力和广泛的分布,某些菌株具有细胞膜上的高分子通道与大质粒,能够降解高分子有机污染物〔尤其是多环芳烃(PAHs)〕.这些特性使得鞘氨醇单胞菌在环境污染治理与生物技术领域具有广阔的应用前景.

优势短杆菌对多环芳烃的降解性能

本研究从长期被焦化废水污染的污泥中分离出一株优势短杆菌 .研究该菌株及其在无机离子存在下对蒽、菲、芘的降解性能 .结果发现该菌株对蒽、菲、芘均有良好的降解效果 ,Fe3 + 对降解过程有促进作用 ,反应 1 0h后 ,蒽、菲、芘转化率分别可达约 75 % ,87% ,及 62 % .总有机碳 (TOC)的测定结果表明 ,该菌株在 1 0 6h内能分别将反应瓶中加入的蒽、菲、芘所产生的总有机碳去除 5 0 %、90 %及 5 0 %

PAHs降解菌的分离、鉴定及降解能力测定

以芴、菲、蒽、芘为碳源和能源筛选、分离PAHs降解菌。14株能降解利用PAHs的菌株被分离。通过HPLC分析,在含芴、菲、蒽、芘的混合培养基质中10号菌的降解能力最强。研究它的降解性能和生长情况,表明该菌在混合反应体系中培养30d后对芴、菲、蒽、芘的降解率分别为95.27、90.46、28和80%;在只含一种PAH的单反应体系中该菌对芴、菲、蒽的降解能力提高,降解率分别可达98.91、94.32和52.17%,而对芘的降解能力则降低,降解率仅为62.47%。与混合PAHs培养体系相比,在单一PAH培养体系中,细菌的对数生长期缩短1/3。经生理生化鉴定和16SrDNA序列对比分析,确定10号菌株属于假单胞菌,命名为PseudomonasspFAP10。

土壤环境中多环芳烃的微生物降解及联合生物修复

研究土壤环境中持久性有机污染物的生物降解及其生物修复技术是当今国际环境修复科学技术前沿领域的重要课题。本文重点论述了土壤环境中持久性有机污染物多环芳烃的微生物降解机理及其在生物修复中的应用等,并结合当前研究进展,展望了基于多种修复措施相结合的多环芳烃污染土壤联合生物修复工程技术的开发与应用前景。

深海多环芳烃降解菌新鞘氨醇杆菌H25的降解特性及降解基因

【目的】为了从深海环境中筛选新的多环芳烃降解菌,了解其降解基因及降解特性。【方法】以原油作为碳源从印度洋深海海水样品中富集筛选出降解能力较强的多环芳烃降解菌,并根据已报道的相关菌属的多环芳烃起始双加氧酶大亚基序列及侧翼序列设计兼并引物进行扩增。【结果】获得了1株能够高效降解原油、柴油及多种多环芳烃的菌株H25。经16SrDNA序列系统发育分析表明它属于新鞘氨醇杆菌属(Novosphingobium)(96%)。并从该菌株中扩增获得2条相似度为91.0%双加氧酶基因片段。2条序列在NCBI上Blastn分析表明均与菌株N.aromaticivorans DSM12444T的降解质粒pNL1上的双加氧酶大亚基具有最高相似度,分别为99.6%和91.0%。根据pNL1上的双加氧酶序列设计引物获得了包含H25双加氧酶大亚基及上下游序列的2个基因片段H25Ⅰ(2.9kb)和H25Ⅱ(4.5kb)。另外,单碳降解实验表明H25对联苯、2-甲基萘、2,6-二甲基萘、菲、二苯并噻吩、二苯并呋喃等均有较好的降解能力。【结论】H25菌株是Novosphingobium属可能的新种。深海细菌在大洋环境多环芳烃污染的自然净化中起到一定作用,并在环境生物修复中有较大的应用前景。

堆制处理过程中的多环芳烃降解

用实验室模拟方法，研究了堆制处理过程对污染土壤中４ ～６ 环的多环芳烃（ＰＡＨｓ） 的降解． 结果表明，堆制对６ 种难降解的ＰＡＨｓ 都有不同程度的降解作用，ＰＡＨｓ 的降解随着苯环数的增加而降低，其去除率的大小顺序为荧蒽＞ 苯并［ａ］ 蒽、苯并［ａ］ 芘＞ 苯并［ｂ］ 荧蒽、苯并［ｋ］ 荧蒽＞ 苯并［ｇｈｉ］ 北． 其中，荧蒽的去除率为４６．０ ％ ～９２．９％ ；苯并［ａ］ 蒽的去除率为７．７％ ～３７ ．２ ％ ． 当ＰＡＨｓ 的初始浓度提高约５０ 倍时，除荧蒽外其它ＰＡＨｓ 的降解随着污染浓度的提高而降低． 不同Ｃ／Ｎ均有类似的规律，但Ｃ／Ｎ２５：１ 比Ｃ／Ｎ４０：１ 为好． 堆中各种ＰＡＨｓ 浓度在高温期以前都有所提高，但在降温期以后又有不同程度的降低． 细菌总数测定表明，数量变化呈双峰型．

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。