1，4-二氯苯降解菌的分离及其降解特性研究

从某污水处理曝气池的活性污泥中分离出一株能够以1,4-二氯苯为唯一碳源和能源生长的菌株DEB-1,通过形态特征和生理生化试验初步鉴定为黄杆菌属（Flavobacterium sp.）。实验结果表明,该菌株最适降解温度为32℃、最适降解pH为7.8,24 h对100 mg/L的1,4-二氯苯的降解率达94.5%。菌株DEB-1的降解谱较广,对5种氯苯类物质具有较高的降解率。并进一步研究了DEB-1的1,4-二氯苯降解酶粗酶液的性质,其最适反应温度和pH分别为30℃和8.5。对处理含氯代芳香化合物的有机废水具有一定的意义。     

苯胺降解菌的分离和降解特性研究

通过驯化富集培养,从白洋淀底泥中分离筛选出数株能够有效降解苯胺的菌株,经过反复筛选,得到一株能够以苯胺为唯一碳源、高效降解苯胺的菌株BA-1-3.其利用苯胺的最适pH值为7.0,最适温度为30℃,在苯胺浓度为1000 mg/L,180 r/min条件下振荡培养60 h,降解率达到80%以上.经鉴定,菌株BA-1-3属苍白杆菌属(Ochrobactrumsp.).     

一株耐盐柴油降解菌的分离鉴定及其降解性能

从某油田附近受石油污染土壤中分离出一株以柴油为惟一碳源的耐盐菌株LS1。通过对菌株的生理生化特性、菌体的形态观察及16S r DNA基因序列分析鉴定菌株LS1为假单胞菌属(pseudomonas)。该菌株可耐受的最高盐度(Na Cl)和柴油浓度分别为6%~8%和12 000 mg/L。菌株生长的适宜p H和温度条件分别为6.0~8.0和28~36℃。在盐度为6%、p H为7.0、温度为32℃、菌种投加量为10%的条件下,初始浓度为3 000 mg/L的柴油经6 d降解后,去除率可达78.3%,加入适量外加碳源葡萄糖和蔗糖,可使降解率分别提高至92%和90%左右。菌株LS1的耐盐机理可能是通过在细胞内积累甜菜碱以调节菌株细胞内外渗透压平衡。投加甜菜碱可提高耐盐菌LS1在高盐环境下对柴油的降解效率。     

一株苯胺降解菌的分离及其降解特性

从某城市生活污水处理厂曝气池的活性污泥中分离出一株以苯胺为唯一碳源和氮源的高效降解菌Z1。通过16S r DNA基因序列分析,初步鉴定菌株。结果表明,菌株Z1为假单胞菌(Pseudomonas sp.)。该菌株最适生长和降解条件为p H 6.0~8.0、30℃、盐度0.1%~1.0%。在此条件下,16 h内能够将400 mg/L的苯胺降解完全,且当苯胺初始浓度为1 300 mg/L时,苯胺的最大降解速率为41.4 mg/(L·h),32 h内降解率达到98%。菌株对苯胺的最大耐受浓度为1 800mg/L。当苯胺和苯酚共存时,苯胺的降解效果随着苯酚浓度的增大而减小,当苯酚浓度达到370 mg/L时,Z1无法降解苯胺。添加氯化铵做外加氮源能解决高浓度苯酚和苯胺共降解的问题。在苯胺降解过程中大约有43%苯胺态氮转化成氨氮释放到环境中。     

Fe2+活化过硫酸钠降解1,2-二氯苯

以Na2S2O8为氧化剂,柠檬酸螯合Fe2+为活化剂,对水中1,2-二氯苯进行处理。首先研究了Na2S2O8浓度、FeSO4浓度、柠檬酸浓度及初始pH值等因素对1,2-二氯苯降解的影响;然后通过正交实验,发现在Na2S2O8浓度14.28 mmol/L、FeSO4浓度7.14 mmol/L、柠檬酸浓度3.57 mmol/L、初始pH值3.0的条件,1,2-二氯苯降解率达到最大(99.28%)。进一步研究表明,柠檬酸螯合FeSO4活化Na2S2O8降解1,2-二氯苯的过程可分为2个阶段,其中第1阶段为快速反应,第2阶段反应速度较慢并且符合一级反应动力学规律。     

微囊藻毒素-LR降解菌的筛选及降解特性研究

从上海市淀山湖表层水体中筛选分离出了1株降解微囊藻毒素-LR(MC-LR)的细菌并研究了其降解特性。根据细胞形态结构、生理生化特征及其16S rDNA基因序列分析,鉴定分离菌株DHU-28(GenBank序列登录号为HM047512)属嗜麦芽寡养单胞菌(Stenotrophomonas maltophilia)。微囊藻毒素降解实验结果表明,该菌株能在以MC-LR为唯一碳源、氮源的无机盐培养基中生长,6 d内可将初始质量浓度为15 mg/L的MC-LR降解为8.12 mg/L,降解效率达到45.9%。菌株DHU-28的最适生长温度是30℃,最适生长pH为7.0。酵母粉、蛋白胨、葡萄糖等营养物质可以明显促进菌株对MC-LR的降解效率,尤其是加入50 mg/L酵母粉后,6 d降解率达到63.2%。     

一株对硝基苯酚降解菌的筛选鉴定及其降解特性

从受甲基对硫磷污染的土壤中分离筛选得到一株能够以对硝基苯酚(PNP)作为唯一碳源、氮源生长的菌株,命名为TM.经16S rDNA序列分析初步鉴定该菌株为节杆菌(Arthrobacter).考察了该菌株在PNP浓度、盐度(NaCl)、pH、外加碳源(葡萄糖)、外加氮源等因素下对PNP降解特性的影响.结果表明:该菌株对PNP的最大耐受质量浓度为300 mg/L,并在降解的过程中生成NO2-该菌株的耐盐能力可达0.30％(质量分数),其最佳pH为8.在此pH下,200 mg/L的PNP在16h时即可被完全降解,添加0.30％(质量分数)的葡萄糖可使生物量和降解速率达到最大,牛肉膏作为外加氮源最有利于该菌株对PNP的降解.     

萘降解菌的分离鉴定、生长特性和降解途径探究

从天津大港油田附近污染土壤中分离出1株萘降解菌株DGN9,经形态学和16S rDNA测序鉴定,该菌株属于无色杆菌(Achromobacter sp.)。其最适生长温度为30℃,最适pH为7,最适萘初始质量浓度为1 000mg/L,在NaCl质量分数为1%、2%的条件下生长良好,具有一定的耐盐性。其对萘的可能降解途径为水杨酸降解途径。同时,该菌株对蒽、菲、芘、联苯、对苯二甲酸、邻苯二酚、苯酚、苯甲酸钠、水杨酸、邻苯二甲酸等底物也有降解作用,具有底物生长广谱性。     

甲氰菊酯降解菌鉴定及其降解特性

从农药厂污泥中分离到一株能降解甲氰菊酯的光合细菌PSB07-19.鉴定结果表明,PSB07-19为沼泽红假单胞菌(Rhodopseudomonas palustris),其最适生长温度为30℃,最适pH为6.5.实验结果表明,该菌以共代谢方式降解甲氰菊酯,对甲氰菊酯的最大耐受质量浓度为600 mg/L,培养15 d对400 mg/L甲氰菊酯的降解率达45.51%,降解最适pH、温度分别为7.5、30℃.     

1,1-二氯乙烯降解菌的分离鉴定及降解特性

从好氧活性污泥中分离得到一株能以1,1-二氯乙烯(1,1-DCE)作为惟一碳源和能源生长的革兰氏阴性菌株D-B,经鉴定属于产碱杆菌属(Alcaligenessp.)。当维持菌株D-B浓度一定时,1,1-DCE的去除率随着1,1-DCE浓度的增大先增加后降低,且降解过程主要发生在加入1,1-DCE后的3~5 h内。当1,1-DCE的初始浓度为300μg/L时去除率达到最大值85.32%。菌株D-B对1,1-DCE的降解符合Monod方程,饱和常数Ks=21.96 mg/L,1,1-DCE的最大比基质降解速率Vmax=50.76 mg/(L.h)。     

Catalytic destruction of 1,2-dichlorobenzene on V2O5-WO3/Al2O3-TiO2 catalyst

Studies on the catalytic destruction of 1,2-dichlorobenzene were carried out on a specially constructed semi-technical equipment whose most important element was a catalytic reactor with a monolithic catalyst in the form of 150 x 150 x 100 mm cubes. A catalyst made from cordierite with an active layer composed of Al2O3 - 64 wt%, TiO2 - 26 wt%, V2O5 - 6.6 wt% and WO3 - 3.4 wt% was used. The reactor made it possible to carry out the process in the temperature range 150-350 degrees C, at variable catalyst loading and different velocities of gas flow through the reactor. The content of 1,2-dichlorobenzene in the air was analysed by a chromatographic method. A significant effect of catalyst loading and temperature on 1,2-dichlorobenzene destruction efficiency was observed and no effect of the linear flow velocity through the catalyst on o-dichlorobenzene destruction efficiency was reported. The applied vanadium-tungsten catalyst on a monolithic carrier made from TiO2/gamma-Al2O3 revealed very good activity that resulted in an over 80% efficiency of 1,2-dichlorobenzene destruction at the temperature around 250 degrees C at a very high catalyst loading reaching ca. 8200 h(-1). Additionally, in this study the kinetics of 1,2-dichlorobenzene decomposition was determined, specifying the order of reaction and dependence of the decomposition rate constant on temperature, using a simple power-rate law model.     

微囊化生物流化床处理邻二氯苯废水

采用海藻酸钠—壳聚糖—活性炭(SA-CA-PAC)生物微胶囊包埋优势降解菌用于生物流化床处理邻二氯苯废水。比较了微囊化菌和悬浮菌对废水的降解效果,同时考察了初始浓度、接种量、pH值、温度和曝气量对降解率的影响。结果表明,微囊化菌比悬浮菌拥有更适宜的生长环境,具有更好的pH稳定性和热稳定性。微囊化菌的降解效果优于悬浮菌,处理150 mg/L的邻二氯苯废水的最佳接种量为10%,最适pH为7.5,最适温度为30℃。     

Degradation of chlorobenzenes by a strain of Acidovorax avenae isolated from a polluted aquifer

A subsurface microbial community was isolated from a polluted site of Suquía River (Córdoba-Argentina), acclimated during 15 days in aerobic conditions using 1,2-dichlorobenzene (1,2-DCB) as the sole carbon source. From this acclimated community, we isolated and identified by 16S rDNA analysis a strain of Acidovorax avenae, which was able to perform the complete biodegradation of 1,2-DCB in two days affording stoichiometric amounts of chloride. This pure strain was also tested for biodegradation of chlorobenzene (CB); 1,3-DCB and 1,4-DCB, giving similar results to the experiments using 1,2-DCB. The aromatic-ring-hydroxylating dioxygenase (ARHDO) alpha-subunit gene core, encoding the catalytic site of the large subunit of chlorobenzene dioxygenase, was detected by PCR amplification and confirmed by DNA sequencing. These results suggest that the isolated strain of A. avenae could use a catabolic pathway, via ARHDO system, leading to the formation of chlorocatecols during the first steps of biodegradation, with further chloride release and subsequent paths that showed complete substrate consumption.     

The fate of chlorobenzenes and permethrins during anaerobic sewage sludge digestion

Mixed primary sewage sludge was incubated anaerobically with and without azide addition to prevent biological activity. The behaviour of 1,3-, 1,4- and 1,2-dichlorobenzene, 1,3,5-, 1,2,4- and 1,2,3-trichlorobenzene, 1,2,3,4- and 1,2,4,5-tetrachlorobenzene, hexachlorobenzene, and cis- and trans-permethrin was examined to determine their potential removal during anaerobic digestion. All the chlorobenzenes were removed to varying extents over 32 days of incubation, ranging from 25% removal for 1,3,5-trichlorobenzene to 80% removal for 1,4-dichlorobenzene. Biodegradation may have been responsible for the reductions in 1,3- and 1,4-dichlorobenzene and 1,2,4- and 1,2,3-trichlorobenzene as there was no significant removal of these compounds in azide treated sludge. The removal over 32 days of cis- and transpermethrin was 87% and 96% respectively. These removals were attributed to a chemical or physical process.     

Simulation model for biotransformation of xenobiotics and chemotaxis in soil columns

In this paper a model is presented which can be used to simulate the behaviour of xenobiotic chemicals in soil columns with respect to their physical and chemical properties. Terms describing biological transformation of xenobiotics are also included in the model. It incorporates microbial growth following Monod kinetics and a chemotactic response of the transforming bacteria towards the xenobiotic substrate. The model appeared to yield good simulations of an experiment by Van der Meer et al. (1987) who investigated the degradation of 1,2-dichlorobenzene in soil columns inoculated with Pseudomonas sp. strain P51. The behaviour and the fate of 1,4-dichlorobenzene as found by Kuhn et al. (1985) can also be simulated using this model but their results were also adequately simulated using a simple second order model. The results generated by the model correspond to kinetic parameters obtained in other studies. It is concluded that the model is a useful tool for the investigation of the activity of bacteria degrading xenobiotics in soil columns, provided that the microbial parameters can be determined in independent experiments, and that the active microbial mass in the soil can be measured.     

Bioconcentration and uptake kinetics of chlorobenzenes in soy-bean roots

Excised soy-beanroots were exposed to an aqueous solution of five homologous chlorobenzenes in constant concentration. The results were in general agreement with water-lipid partitioning. The relationship between the bioconcentration factor and the octanol-water partition coëfficiënt (K_OW) can be used to estimate bioconcentration. Effective equilibrium was reached within 2.5 hours for 1,2-di-, 1,3,5-tri- and 1,2,3,4-hexachlorobenzene and after a mean of 10.1 and 17.9 hours for penta- and hexachlorobenzene respectively. For 1,2-dichlorobenzene, 1,3,5-trichlorobenzene and 1,2,3,4-tetrachlorobenzene the elimination rate constant was > 4.1, and 0.46 and 0.30 hr⁻¹ for penta- respectively hexachlorobenzene. In the range log K_ow 4.56–5.77, k₂ was negatively correlated with log K_OW but k₁ was not correlated with log K_OW..     

Benzoate degradation by Rhodococcus opacus 1CP after dormancy: Characterization of dioxygenases involved in the process

The process of benzoate degradation by strain Rhodococcus opacus 1CP after a five-year dormancy was investigated and its peculiarities were revealed. The strain was shown to be capable of growth on benzoate at a concentration of up to 10 g L^?1. The substrate specificity of benzoate dioxygenase (BDO) during the culture growth on a medium with a low (200–250 mg L^?1) and high (4 g L^?1) concentration of benzoate was assessed. BDO of R. opacus 1CP was shown to be an extremely narrow specificity enzyme. Out of 31 substituted benzoates, only with one, 3-chlorobenzoate, its activity was higher than 9% of that of benzoate. Two dioxygenases, catechol 1,2-dioxygenase (Cat 1,2-DO) and protocatechuate 3,4-dioxygenase (PCA 3,4-DO), were identified in a cell-free extract, purified and characterized. The substrate specificity of Cat 1,2-DO isolated from cells of strain 1CP after the dormancy was found to differ significantly from that of Cat 1,2-DO isolated earlier from cells of this strain grown on benzoate. By its substrate specificity, the described Cat 1,2-DO was close to the Cat 1,2-DO from strain 1CP grown on 4-methylbenzoate. Neither activity nor inhibition by protocatechuate was observed during the reaction of Cat 1,2-DO with catechol, and catechol had no inhibitory effect on the reaction of PCA 3,4-DO with protocatechuate.     

Naphthalene metabolism in Nocardia otitidiscaviarum strain TSH1, a moderately thermophilic microorganism

The thermophilic bacterium Nocardia otitidiscaviarum strain TSH1, originally isolated in our laboratory from a petroindustrial wastewater contaminated soil in Iran, grows at 50 degrees C on a broad range of hydrocarbons. Transformation of naphthalene by strain TSH1 which is able to use this two ring-polycyclic aromatic hydrocarbon (PAH) as a sole source of carbon and energy was investigated. The metabolic pathway was elucidated by identifying metabolites, biotransformation studies and monitoring enzyme activities in cell-free extracts. The identification of metabolites suggests that strain TSH1 initiates its attack on naphthalene by dioxygenation at its C-1 and C-2 positions to give 1,2-dihydro-1,2-dihydroxynaphthalene. The intermediate 2-hydroxycinnamic acid, characteristic of the meta-cleavage of the resulting diol was identified in the acidic extract. Apart from typical metabolites of naphthalene degradation known from mesophiles, benzoic acid was identified as an intermediate for the naphthalene pathway of this Nocardia strain. Neither phthalic acid nor salicylic acid metabolites were detected in culture extracts. Enzymatic experiments with cell extract showed the catechol 1,2-dioxygenase activity while transformation of phthalic acid and protocatechuic acid was not observed. The results of enzyme activity assays and identification of benzoic acid in culture extract provide strong indications that further degradation goes through benzoate and beta-ketoadipate pathway. Our results indicate that naphthalene degradation by thermophilic N. otitidiscaviarum strain TSH1 differs from the known pathways found for the thermophilic Bacillus thermoleovorans Hamburg 2 and mesophilic bacteria.     

Investigation of organic xenobiotic transfers,partitioning and processing in air-soil-plant systems using a microcosm apparatus. Part II: comparing the fate of chlorobenzenes in grass planted soil

A microcosm system was used to investigate and compare transfers of 14C labeled-1,2-dichlorobenzene (DCB), 1,2,4-trichlorobenzene (TCB) and hexachlorobenzene (HCB) in an air-soil-plant system using single grass tillers planted into spiked soil. This study was the second phase of a development investigation for eventual study of a range of xenobiotic pollutants. Recoveries from the system were excellent at >90%. The predominant loss pathway for 14C labeled-1,2-DCB and 1,2,4-TCB was volatilisation with 85% and 76% volatilisation of parent compound and volatile metabolites over 5 weeks respectively. Most of the added label in the hexachlorobenzene spiked system remained in soil. Mineralisation was <1% for all compounds. 14C plant burdens expressed as microg parent compound/g plant fresh weight were significant and suggest that plant uptake of chlorobenzenes from soil may be an important exposure pathway for grazing herbivores. Both shoot and root uptake of 14C was detected, with foliar uptake of volatilised compounds dominating shoot uptake, and being greatest in TCB spiked systems. The microcosm is shown as potentially an ideal system with which to investigate organic xenobiotic partitioning in air-soil-plant systems to improve understanding of the equilibria and kinetics of exchanges. However, limitations imposed by the lab based conditions must be recognized and data should be compared with field based data sets as a consequence.