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2.
Pollution of soil with heavy metals, herbicides, antibiotics and other chemicals is known to have a negative effect on microbial activities. Therefore, the aim of this study was to isolate cultures of Azotobacter sp. from polluted and unpolluted soils and to study the effect of these pollutants on their growth. A total of 120 Azotobacter sp. were isolated from soils irrigated with wastewater (contaminated soils) and groundwater (uncontaminated soils). These isolates were screened for resistance to heavy metals, herbicide and antibiotics. Also, the soils from which the cultures were isolated were analyzed for the concentrations of Zn 2+, Cd 2+, Cu 2+, Pb 2+ and Mn 2+ they contained. Contaminated soil showed high levels of heavy metals as compared to uncontaminated soil. The size of the Azotobacter population in contaminated soil was lower than that in uncontaminated soil. Of the Azotobacter isolates, 64 that were recovered from contaminated soil exhibited high resistance to heavy metals (Hg 2+, Cd 2+, Cu 2+, Cr 3+, Co 2+, Ni 2+, Zn 2+ and Pb 2+) and herbicide 2,4-D compared to 56 isolates from uncontaminated soil. Also, isolates from contaminated soil showed high resistance to chloramphenicol, nitrofurantoin and co-trimoxazole compared to those isolated from uncontaminated soil. The majority of Azotobacter isolates from contaminated soil showed multiple-resistance to different metal ions and antibiotics. All isolates failed to grow at pH less than 6. Salt concentration (5%) was found to be inhibitory to all isolates. The most potent isolates from contaminated soil that showed multiresistance to all substances tested were identified on the basis of morphological and biochemical characteristics, and 16S rRNA as A. chroococcum. These resistant isolates could be employed in contaminated soils and/or bioremediation. 相似文献
3.
Industrial wastewaters contain various heavy metal components and therefore threaten aquatic bodies. Heavy metals can be adsorbed by living or non‐living biomass. Submerged aquatic plants can be used for the removal of heavy metals. This paper exhibits the comparison of the adsorption properties of two aquatic plants Myriophyllum spicatum and Ceratophyllum demersum for lead, zinc, and copper. The data obtained from batch studies conformed well to the Langmuir Model. Maximum adsorption capacities ( qmax) were obtained for both plant species and each metal. The maximum adsorption capacities ( qmax) achieved with M. spicatum were 10.37 mg/g for Cu 2+, and 15.59 mg/g for Zn 2+ as well as 46.49 mg/g for Pb 2+ and with C. demersum they were 6.17 mg/g for Cu 2+, 13.98 mg/g for Zn 2+ and 44.8 mg/g for Pb 2+. It was found that M. spicatum has a better adsorption capacity than C. demersum for each metal tested. Gibbs free energy and the specific surface area based on the qmax values were also determined for each metal. 相似文献
4.
In this study, dried and humid fruiting bodies of Tremella fuciformis and Auricularia polytricha were examined as cost-effective biosorbents in treatment of heavy metals (Cd 2+, Cu 2+, Pb 2+, and Zn 2+) in aqueous solution. The humid T. fuciformis showed the highest capacity to adsorb the four metals in the multi-metal solutions. The Pb 2+ adsorption rates were 85.5%, 97.8%, 84.8%, and 91.0% by dried T. fuciformis, humid T. fuciformis, dried A. polytricha, and humid A. polytricha, respectively. The adsorption amount of Pb 2+ by dried and humid T. fuciformis in Cd 2+ + Pb 2+, Cu 2+ + Pb 2+, Pb 2+ + Zn 2+, Cd 2+ + Cu 2+ + Pb 2+, and Cd 2+ + Zn 2+ + Pb 2+ solutions were not lower than that in Pb 2+ solutions. The results suggested that in humid T. fuciformis, Cd 2+, Cu 2+, and Zn 2+ promoted the Pb 2+ adsorption by the biomass. In the multi-metal solutions of Cd 2+ + Cu 2+ + Pb 2+ + Zn 2+, the adsorption amount and rates of the metals by all the test biosorbents were in the order of Pb 2+ > Cu 2+ > Zn 2+ > Cd 2+. Compared with the pseudo first-order model, the pseudo second-order model described the adsorption kinetics much better,
indicating a two-step biosorption process. The present study confirmed that fruiting bodies of the jelly fungi should be useful
for the treatment of wastewater containing Cd 2+, Cu 2+, Pb 2+, and Zn 2+. 相似文献
5.
A bench study was carried out to characterize the kinetics of two plant growth promoting rhizobacteria (PGPR) Azotobacter chroococcum and Bacillus megaterium to adsorb heavy metals from solution. Adsorption of Pb 2+ and Cd 2+ by bacterial cells was processed quickly with an equilibration achieved within 5 min. The adsorptions were fitted well with Freundlich and Langmuir isotherm models. The comparison of isotherm parameters indicated that A. chroococcum had a stronger capacity to bind metal ions than B. megaterium, with an average increase of 59.8% for Pb 2+ and 75.6% for Cd 2+, respectively. Both bacteria had a stronger affinity to Pb 2+ than Cd 2+ since Pb 2+ was more easily bound with the phosphoryl groups on the cell surface than Cd 2+. This demonstrated that the presence of bacteria in the rhizosphere may result in the reduction of mobile ions in soil solution. 相似文献
6.
In this work we isolated from soil and characterized several bacterial strains capable of either resisting high concentrations
of heavy metals (Cd 2+ or Hg 2+ or Pb 2+) or degrading the common soil and groundwater pollutants MTBE (methyl- tert-butyl ether) or TCE (trichloroethylene). We then used soil microcosms exposed to MTBE (50 mg/l) or TCE (50 mg/l) in the presence
of one heavy metal (Cd 10 ppm or Hg 5 ppm or Pb 50 or 100 ppm) and two bacterial isolates at a time, a degrader plus a metal-resistant
strain. Some of these two-membered consortia showed degradation efficiencies well higher (49–182% higher) than those expected
under the conditions employed, demonstrating the occurrence of a synergetic relationship between the strains used. Our results
show the efficacy of the dual augmentation strategy for MTBE and TCE bioremediation in the presence of heavy metals. 相似文献
7.
Environmental pollution with toxic heavy metals is increasing throughout the world alongside industrial development. Microorganisms and microbial products can be highly efficient bioaccumulators of soluble and particulate forms of metals, especially dilute external solutions. Microbe related technologies (Biotechnology) may provide an alternative or additive conventional method for metal removal or metal recovery. This study dealt with isolation, identification and characterization of heavy metal-resistant (Pb 2+, Cd 2+, Al 3+, Cu 2+, Ag 2+ and Sn 2+) bacteria from sewage wastewater at Taif Province, Saudi Arabia. Nine bacterial isolates were selected by using an enrichment isolation procedure based on high level of heavy metal resistance. All the isolates showed high resistance to heavy metals with Minimum Inhibitor Concentration (MIC) ranging from 800 μg/ml to 1400 μg/ml. All nine resistant isolates showed multiple tolerances to heavy metals. On the basis of morphological, biochemical and 16S rRNA characterization, the most potent isolates (Cd1-1, Ag1-1, Ag1-3 and Sn1-1) were identified as Alcaligenes faecalis. Scanning electron microscope analysis showed that the morphology of Alcaligenes faecalis Ag1-1 was unchanged after growth in medium without and with addition of Ag 2+ indicative Ag 2+ is not toxic to the isolate under the conditions tested. The ability of Alcaligenes faecalis Ag1-1 to synthesize sliver nanoparticles was examined. The heavy metal-resistant bacteria obtained could be useful for the bioremediation of heavy metal-contaminated environment. 相似文献
8.
To assess the potential of Pb +2 accumulation in different parts of Acacia victoria, one year old A. victoria seedlings were exposed to Pb 2+(NO 3) 2 in 5 different concentrations: 0, 50, 250, 500 and 1000 (mg Pb 2+ L ?1) for 45 days. Subsequently, Pb 2+ uptake was quantified in roots, shoots and leaves of the seedlings by Atomic Absorption Spectroscopy (AAS). In addition, some physiological parameters such as biomass production, shoots and roots length, plant appearance, tissue concentrations and chlorophyll content were examined. Tissue concentrations increased as Pb 2+ concentration increased for A. victoria. The visible toxicity symptoms (chlorosis and necrosis) appeared only to the highest concentration (1000 mg Pb 2+ L ?1), resulting in photosynthesis decrease, plant height, root length and dry biomass reduction. Almost 70% (up to 3580 mg Kg ?1 of dry tissue) from the Pb 2+ was accumulated in the entire plant tissues was retained in the roots in the seedlings exposed to 1000 mg Pb 2+ L ?1. The seedlings accumulated between 403 to 913 mg Kg ?1 of Pb 2+ in shoots and 286 to 650 mg Kg ?1 of Pb 2+ in leaves at different treatments. Bioconcentration and translocation factors were determined 5.14 and 0.255, respectively. The results show that A. victoria is suitable for lead-phytostabilization in Pb 2+-contaminated soil. 相似文献
9.
Many polluted sites are simultaneously contaminated with polycyclic aromatic hydrocarbons and heavy metals. In the present study, batch and continuous column experiments were performed utilizing self-composition soil to describe the sorption behavior of two contaminants: lead (Pb 2+) and pyrene (PYR). Operational conditions such as contact time, bed depth, and flow rate were optimized. The effect of soil organic matter content on the process of adsorption of both contaminants was investigated. The presence of PYR in solution at neutral pH (6.0–7.5) decreased Pb 2+ sorption. Similar behavior was observed for PYR in the presence of Pb 2+ in solution. At room temperature, batch experimental data conducted as a function of contact time were analyzed using the Langmuir and Freundlich isotherms. Results revealed that Pb 2+ sorption isotherms were fitted better by the Langmuir model and PYR sorption isotherms were fitted better by the Freundlich model. Column adsorption experiments were carried out at room temperature and under operating parameters (bed depth, flow rate, and initial contaminant concentration). Breakthrough curves were well fitted to the two-site first-order kinetic model with a sum of square errors less than 0.14. The Pb 2+ adsorption kinetic data were processed also for the Thomas model with a good accuracy. 相似文献
10.
Removal of heavy metals (Pb 2+, Zn 2+) from aqueous solution by dried biomass of Spirulina sp. was investigated. Spirulina rapidly adsorbed appreciable amount of lead and zinc from the aqueous solutions within 15 min of initial contact with the
metal solution and exhibited high sequestration of lead and zinc at low equilibrium concentrations. The specific adsorption
of both Pb 2+ and Zn 2+ increased at low concentration and decreased when biomass concentration exceeded 0.1 g l −1. The binding of lead followed Freundlich model of kinetics where as zinc supported Langmuir isotherm for adsorption with
their r
2
values of 0.9659 and 0.8723 respectively. The adsorption was strongly pH dependent as the maximum lead biosorption occurred
at pH 4 and 10 whereas Zn 2+ adsorption was at pH 8 and 10. 相似文献
11.
A zinc-resistant bacterium, Brevibacterium sp. strain HZM-1 which shows a high Zn 2+-adsorbing capacity, was isolated from the soil of an abandoned zinc mine. Kinetic analyses showed that Zn 2+ binding to HZM-1 cells follows Langmuir isotherm kinetics with a maximum metal capacity of 0.64 mmol/g dry cells and an apparent
metal dissociation constant of 0.34 mM. The observed metal-binding capacity was one of the highest values among those reported
for known microbial Zn 2+ biosorbents. The cells could also adsorb heavy metal ions such as Cu 2+. HZM-1 cells could remove relatively low levels of the Zn 2+ ion (0.1 mM), even in the presence of large excess amounts (total concentration, 10 mM) of alkali and alkali earth metal
ions. Bound Zn 2+ ions could be efficiently desorbed by treating the cells with 10 mM HCl or 10 mM EDTA, and the Zn 2+-adsorbing capacity of the cells was fully restored by treatment of the desorbed cells with 0.1 M NaOH. Thus, HZM-1 cells
can serve as an excellent biosorbent for removal of Zn 2+ from natural environments. The cells could grow in the presence of significant concentrations of ZnCl 2 (at least up to 15 mM) and thus is potentially applicable to in situ bioremediation of Zn 2+-contaminated aqueous systems.
Received: 1 February 2000 / Received revision: 31 March 2000 / Accepted: 1 May 2000 相似文献
12.
We compared the performance of aerobic Cr(VI)-reducing bacteria isolated from Cr(VI)-contaminated soil in pure and mixed cultures of five isolated strains. The mixed culture had increased reduction rates compared to individual cultures. Cr(VI) reduction was observed in sterile soil inoculated with Pseudomonas fluorescens and in non-sterile soil with and without inoculation with P. fluorescens at initial pore water concentrations up to 1,600 mg Cr(VI)/L, whereas in culture the maximum inhibitory concentration was 500 mg Cr(VI)/L. Linear rates of Cr(VI) reduction in non-sterile soil amended with peptone were ~5 to 8 times higher than those observed in the mixed culture. Inoculation of non-sterile soil with P. fluorescens did not further enhance Cr(VI) reduction rates. Our results indicate that evaluation of Cr(VI) reduction capacity in Cr(VI)-contaminated soil for in-situ bioremediation purposes should not be done solely in pure culture. Although the latter may be used initially to assess the effects of process parameters (e.g., pH, temperature), the rate and extent of Cr(VI) reduction should be determined in soil for bioremediation design purposes. 相似文献
13.
【目的】为缓解重金属废水污染对全球食品安全和人类健康的威胁,降低铅(plumbum, Pb)在土壤及动植物体内的积累,借助固定化技术提高菌株的重金属去除效率。【方法】以白腐真菌(white rot fungi)为实验材料,通过混菌兼容性及铅离子(Pb 2+)去除能力筛选出吸附效果好且兼容性优的复合菌种,探究最优混菌类型及其比例,优化菌球最佳固定化助剂配方,在此基础上深入探究菌球在实际应用中的最优吸附条件。【结果】黄孢原毛平革菌(Phanerochaete chrysosporium)、云芝(Coriolus versicolor)、凤尾菇(Lentinus sajor-caju)和平菇(Pleurotus ostreatus) 4种菌株兼容效果佳,可进行后续实验;其中云芝和凤尾菇以体积1:1混合后对Pb 2+去除效果显著优于各单菌作用;固定化条件优化实验中,20.0 g/L海藻酸钠、15.0 g/L生物炭和2.0×10 6个/mL白腐真菌组成混菌体系,辅以二氧化硅及沸石制得的固定化菌球在96 h Pb 2+... 相似文献
14.
Summary To investigate the interactions of heavy metals with cells, a minimal medium for the growth of enteric bacteria using glycerol-2-phosphate as the sole phosphorus source was developed that avoided precipitation of Pb 2+ with inorganic phosphate. Using this medium, spontaneous mutants of Escherichia coli resistant to addition of Pb(NO 3) 2 were isolated. Thirty-five independent mutants all conferred a low level of resistance. Disk diffusion assays on solid medium were used to survey the response of E. coli and Salmonella typhimurium mutants altered in global regulatory networks to Pb(NO 3) 2) and CdCl 2. Strains bearing mutations in oxyR and rpoH were the most hypersensitive to these compounds. Based upon the response of strains completely devoid of isozymes needed to inactivate reactive oxygen species, this hypersensitity to lead and cadmium is attributable to alteration in superoxide dismutase rather than catalase levels. Similar analysis of chaperonedefective mutants suggests that these metals damage proteins in vivo. 相似文献
15.
The nature chestnut endothelium, as waster source from chestnut ( Castaneamollissima) has pigment effecting the process of adsorbing heavy metalions, and the decolorized endothelium has low adsorption capacity. In order to raise the adsorption capacity of heavy metal ions, the discolor endothelium was pretreated by acidic formaldehyde, cis-butenedioic acid and irradiation. Thermodynamic and kinetics model was fitted to the adsorption of Pb (II) and Cd(II) ions onto modified chestnut endothelium by cis-butenedioic acid. Three independent variables including pH, adsorption time and contact temperature were selected as affecting factors to Response Surface. The modified experiment results showed adsorption rate of Pb(II) and Cd(II) ions on the chestnut endothelium modified by 0.5?mol/L cis-butenedioic acid was higher than other modified methods. Thermodynamic and kinetics model was fitted with Langmuir and Pseudo-second-order kinetic model, respectively. 59.23?°C of the adsorption temperature, the 5.72?h of adsorption time and the 6.16 of pH are the optimized conditions of the adsorption rate of Pb 2+ on modified chestnut endothelium. 55.93?°C of the adsorption temperature, the 4.43?h of adsorption time and the 6.06 of pH are the optimized adsorption conditions of Cd 2+. Under the optimized condition, the experiment value of the adsorption of Pb 2+ and Cd 2+ was 99.76% and 98.90%, respectively, which are close to the predicted value. The FTIR indicated that CO, OH and CH involved in the adsorption process of Pb 2+ and Cd 2+. 相似文献
16.
[目的] 探究镉吸附细菌是否能够高效固定土壤有效镉(Cd),为土壤有效Cd的微生物固定提供理论依据。[方法] 利用含Cd 2+牛肉膏蛋白胨液体培养基对细菌进行Cd的耐受性测试筛选出镉抗性强的菌株;通过16S rRNA基因相似性及系统进化分析鉴定耐镉细菌,将菌细胞加入含CdCl 2溶液中进行Cd 2+吸附效率测定;通过土培模拟实验,测定土壤pH、碱解氮、有效磷、速效钾、有机质、CEC、有效Cd及微生物数量来分析镉吸附细菌对镉污染土壤的影响。[结果] 从德阳鱼腥草根际土壤中分离获得的57株细菌对Cd 2+表现出不同程度的抗性,并从中筛选出3株耐Cd优势细菌普罗威登斯菌属( Providencia)DY8、芽孢杆菌属( Bacillus)DY3和芽孢杆菌属( Bacillus)DY1-4。其对溶液中的Cd 2+表现出较好的吸附作用,吸附效率随着Cd 2+浓度升高而降低。DY8、DY3、DY1-4能使镉污染土壤中有效Cd含量分别降低72.11%、68.55%、62.32%,同时显著提高镉污染土壤中碱解氮、有效磷的含量。[结论] Cd污染农田土壤中含有丰富的耐Cd微生物资源,Cd吸附细菌能降低土壤中有效Cd的含量,且能有效改善土壤养分条件。 相似文献
17.
Heavy metal contamination of the environment is a serious concern because of their deleterious effects on biological systems. To the best of our knowledge, this is the first investigation on isolation of heavy metal resistant bacteria from contaminated sites of glass industrial area. The study focused on isolation and characterization of Ni2+ resistant bacteria from these sites and analysis of their Ni2+ accumulation potential. Out of 38 different bacterial isolates 3 bacteria were able to tolerate up to 24 mM Ni2+ concentration. These bacterial strains were identified as E. coli (AS17b), Escherichia coli (AS21) and Microbacterium sp. (AS33) by 16S rRNA (16S ribosomal RNA) sequencing and their basic local alignment search tool search analysis. Growing cell of E. coli and Microbacterium sp. revealed accumulation of 0.12, 0.08 and 0.06 µg, of Ni2+/mg dry weight of cells, respectively, by 72 hr. Similarly resting cell of these strains showed accumulation of 0.27, 0.11 and 0.08 µg of Ni2+/mg dry weight of cells by 150 min, respectively. These results reveal that strain E. coli (AS21) shows maximum accumulation efficiency for Ni2+ among different isolates studied under shaking as well as starving conditions. Hence, E. coli (AS21) could serve as an efficient and promising bacterium for bioremediation of nickel-contaminated sites. 相似文献
18.
Gene bioaugmentation is a bioremediation strategy that enhances biodegradative potential via dissemination of degradative
genes from introduced microorganisms to indigenous microorganisms. Bioremediation experiments using 2,4-dichlorophenoxyacetic
acid (2,4-D)-contaminated soil slurry and strains of Pseudomonas putida or Escherichia coli harboring a self-transmissible 2,4-D degradative plasmid pJP4 were conducted in microcosms to assess possible effects of
gene bioaugmentation on the overall microbial community structure and ecological functions (carbon source utilization and
nitrogen transformation potentials). Although exogenous bacteria decreased rapidly, 2,4-D degradation was stimulated in bioaugmented
microcosms, possibly because of the occurrence of transconjugants by the transfer of pJP4. Terminal restriction fragment length
polymorphism analysis revealed that, although the bacterial community structure was disturbed immediately after introducing
exogenous bacteria to the inoculated microcosms, it gradually approached that of the uninoculated microcosms. Biolog assay,
nitrate reduction assay, and monitoring of the amoA gene of ammonia-oxidizing bacteria and nirK and nirS genes of denitrifying bacteria showed no irretrievable depressive effects of gene bioaugmentation on the carbon source utilization
and nitrogen transformation potentials. These results may suggest that gene bioaugmentation with P. putida and E. coli strains harboring pJP4 is effective for the degradation of 2,4-D in soil without large impacts on the indigenous microbial
community. 相似文献
19.
By combining two functions of alginate gel and activated carbon, an activated carbon-containing alginate bead (AC-AB) adsorbent was developed and successfully used to simultaneously remove heavy metal ions and toxic organics. Quantitative analysis showed that almost all of the adsorption of toxic organics, such as p-toluic acid, is caused by the activated carbon in the AC-AB adsorbent, whereas the alginate component has a major role in the removal of heavy metals. A 50-L solution containing eight heavy metals (Pb 2+, Mn 2+, Cd 2+, Cu 2+, Zn 2+, Fe 2+, Al 3+ and Hg 2+) and four mineral ions was run continuously through a filter cartridge packed with 160 g of the AC-AB adsorbent. The adsorbent showed a high capacity to remove heavy metals completely from the water, while allowing essential minerals, such as K +, Na +, Mg 2+ and Ca 2+, to pass through the filter. The adsorbent could be regenerated using eluents, such as HNO 3, and reused repeatedly without considerable loss of its metal uptake capacity through 10 subsequent cycles of adsorption and desorption. With its high capacity and high selectivity for toxic heavy metals, the AC-AB adsorbent has enormous potential for application in drinking water treatment technologies. 相似文献
20.
The cyanobacterium Nostoc sphaeroides Kützing is expected to be effective in toxic metal adsorption as it produces abundant exopolysaccharides with functional groups. Therefore, the adsorption properties of Cu 2+, Cd 2+, Cr 3+, Pb 2+, Ni 2+, and Mn 2+ on fresh macrocolonies and algal powder of N. sphaeroides were compared at pH 5 and 25 °C. The adsorption capacity of fresh biomass for Pb 2+ and of algal powder for Pb 2+ and Cr 3+ were highest in single metal solutions. Compared to the fresh biomass, the metal adsorption capacities of algal powder were similar for Ni 2+, Cd 2+, and Pb 2+ and slightly greater for Cr 3+, but they were markedly smaller for Mn 2+ and Cu 2+. Coexisting ions (in tap water or in multiple solutions) significantly decreased the metal adsorption capacity, except for Cr 3+ in tap water. The Pb 2+ and Cr 3+ adsorption dynamic process fitted the pseudo-second-order model well, showing fast adsorption at the first stage in 10 and 20 min, respectively. Higher pH in acidic ranges favored the adsorption greatly. The Langmuir isotherm model was suitable for explaining the adsorption, and the maximum adsorption capacities were 116.28 and 22.37 mg g ?1 for Pb 2+ and Cr 3+, respectively. The adsorption process was endothermic, confirmed by the significantly higher adsorption capability at higher temperature. Hydroxyl, amino, and carboxyl groups were the main functional groups based on Fourier transform infrared spectroscopy analysis, and they bind to metal ions via ion exchange. The results suggest that fresh macrocolonies of N. sphaeroides can be used as an effective biosorbent for metal ion removal, especially for Pb 2+ and Cr 3+. 相似文献
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