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81.
Influence of environmental factors on reductive bioprecipitation of uranium by sulfate reducing bacteria 总被引:2,自引:0,他引:2
Zheng-Ji Yi Kai-Xuan Tan Ai-Li Tan Zhen-Xun Yu Shi-Qiang Wang 《International biodeterioration & biodegradation》2007,60(4):258-266
Microbial reduction of soluble uranyl [U (VI)] to insoluble uraninite by sulfate reducing bacteria (SRB) is a promising remediation strategy for uranium-contaminated groundwater. Effects of environmental factors, including pH and coexisting ions, on U (VI) bioreduction processes (UBP) remain unknown. Anaerobic batch experiments were performed to evaluate impact on UBP. Kinetic investigations with varied pH demonstrated that U (VI) was reduced mostly within 48 h. The bioprecipitation yields depended strongly on pH, increasing from 12.9% to 99.4% at pH 2.0 and 6.0, respectively. Sulfate concentration 4000 mg l−1 did not affect UBP; however, sulfate concentration 5000 mg l−1 significantly slowed UBP. Biogenic H2S produced during sulfate reduction was not directly involved in UBP. At 20 mg l−1 Zn or 10 mg l−1 Cu, no UBP inhibition was observed and uraninite was detected in metal sulfide precipitate. However, 25 mg l−1 Zn or 15 mg l−1 Cu stopped UBP completely. Cu toxicity mechanism probably differed from Zn. The ability to reduce U (VI) was lost permanently with exposure to 15 mg l−1 Cu, but not for Zn 25 mg l−1. No uraninite could be detected before nitrate removal, suggesting nitrate strongly inhibited UBP, which may possibly be related to denitrification intermediates controlling the solution redox potential. 相似文献
82.
Solid lipid nanoparticles (SLN) have been reported to be an alternative system to emulsions, liposomes, microparticles and their polymeric counterparts for various application routes since the early 1990s due to their advantages. Various research groups have also increasingly focused on improving their stability in body fluids after administration by coating of particles with hydrophilic molecules such as poly(ethylene)glycol (PEG) derivatives. Altering surface characteristics by coating SLN with hydrophilic molecules improves plasma stability and biodistribution, and subsequent bioavailability of drugs entrapped. Their storage stability is also increased. This paper basicly reviews types of SLN, principles of drug loading and models of drug incorporation. The influence of PEG coating on particle size and surface characteristics is discussed followed by alteration in pharmacokinetics and bioavailability of drugs in order to target the site of action via SLN. The future direction of research and clinical implications of SLN is also considered. 相似文献
83.
Electron donors for biological sulfate reduction 总被引:8,自引:0,他引:8
Biological sulfate reduction is widely used for treating sulfate-containing wastewaters from industries such as mining, tannery, pulp and paper, and textiles. In biological reduction, sulfate is converted to hydrogen sulfide as the end product. The process is, therefore, ideally suited for treating metal-containing wastewater from which heavy metals are simultaneously removed through the formation of metal sulfides. Metal sulfide precipitates are more stable than metal hydroxides that are sensitive to pH change. Theoretically, conversion of 1 mol of sulfate requires 0.67 mol of chemical oxygen demand or electron donors. Sulfate rich wastewaters are usually deficient in electron donors and require external addition of electron donors in order to achieve complete sulfate reduction. This paper reviews various electron donors employed in biological sulfate reduction. Widely used electron donors include hydrogen, methanol, ethanol, acetate, lactate, propionate, butyrate, sugar, and molasses. The selection criteria for suitable electron donors are discussed. 相似文献
84.
BRASSICA NAPUS was grown under hydroponic conditions and responses to the removal of the external supply of sulfur (S) were analysed in roots and in leaves of different developmental age. The concentrations of sulfate and nitrate were greatest in the older leaves and least in younger leaves, whilst phosphate was greatest in roots and youngest leaves and least in old leaves. S-deprivation resulted in decreases in tissue sulfate concentrations at variable rates in the order: roots and young leaves > middle-aged leaves > oldest leaves. Phosphate concentrations were unaffected and nitrate concentrations were only depleted in the oldest leaves. Expression of representative members of the sulfate transporter gene family was assessed by Northern blotting in the respective tissues. Group 1 transporters (high affinity type) were induced in response to S-deprivation in all tissues except old leaves, where no expression was detected, and to the greatest extent in roots. Groups 2 and 5 (a BRASSICA Group 5 sulfate transporter is reported here, accession number: AJ311389) transporters showed either no or only a small induction by S-deprivation. Group 4 transporters (localised in the tonoplast membrane and thought to be involved in vacuolar sulfate efflux) were induced by S-deprivation with a complex pattern: 4;1 was expressed in root and mature leaves, was strongly induced by sulfur-deprivation in roots, and was also induced in the middle-aged leaves alone; 4;2 was only expressed under S-deprivation in parallel with the observed pattern of tissue sulfate concentrations. Expression patterns indicated that both differences in intracellular sulfate pools and localised aspects of the signal transduction pathway link tissue sulfate-status and sulfur-nutrition regulated gene expression. 相似文献
85.
Baumler DJ Hung KF Jeong KC Kaspar CW 《Extremophiles : life under extreme conditions》2007,11(6):841-851
Acidophiles are typically isolated from sulfate-rich ecological niches yet the role of sulfur metabolism in their growth and
survival is poorly defined. Studies of heterotrophically grown “Ferroplasma acidarmanus” showed that its growth requires a minimum of 100 mM of a sulfate-containing salt. Headspace gas analyses by GC/MS determined
that the volatile sulfur compound emitted by active “F. acidarmanus” cultures is methanethiol. In “F. acidarmanus” cultures grown either heterotrophically or chemolithotrophically, methanethiol was produced constitutively. Radiotracer
studies with 35S-labeled methionine, cysteine, and sulfate showed that all three were used in methanethiol production. Additionally, 3H-labeled methionine was incorporated into methanethiol and was probably used as a methyl-group donor. Methanethiol production
in whole cell lysates supplied with SO32− indicated that NADPH-dependant sulfite reductase and methyltransferase activities were present. Cell lysates also contained
enzymatic activity for methionine-γ-lyase that cleaved the side chain of either methionine to form methanethiol or cysteine
to produce H2S. Since methanethiol was detected from the degradation of cysteine, it is likely that sulfide was methylated by a thiol methyltransferase.
Collectively, these data demonstrate that “F. acidarmanus” produces methanethiol through the metabolism of methionine, cysteine, or sulfate. This is the first report of a methanethiol-producing
acidophile, thus identifying a new contributor to the global sulfur cycle. 相似文献
86.
Acid tolerance of an acid mine drainage bioremediation system based on biological sulfate reduction 总被引:1,自引:0,他引:1
The acid tolerance response of an AMD bioremediation system based on sulfate reduction was investigated. Efficient sulfate reduction was observed with a maximum sulfate reduction rate of 12.3±0.8 mg L(-1) d(-1) and easily available organic carbon was released during high acid treatment with an initial pH of 2.0. The rapid increase in sulfate reduction was observed when the extreme acid treatment with an initial pH of 1.0 was stopped. Column experiment on acid shock showed that efficient sulfate reduction was maintained while precipitation of Cu or Zn still occurred during extreme or high acid shock. More than 98% of Cu and 85% of Zn were removed in the high acid column experiment with influent pH of 2.0. The majority bacteria in the remediation system used for high acid drainage belonged to genera Clostridiaceae, Eubacterium, Pseudobutyrivibrio, and Clostridium. These findings showed high acid tolerance of the straw remediation system. 相似文献
87.
K.I. Kostyanovsky G.K. EvanyloK.K. Lasley W.L. DanielsC. Shang 《Ecological Engineering》2011,37(11):1765-1771
Biosolids deep row incorporation (DRI) offers an alternative recycling approach for bioenergy crop production, but phosphorus additions in excess of the vegetation requirements can potentially impair water quality. The effects of DRI of anaerobically digested (AD) and lime-stabilized (LS) biosolids at four rates (213, 426 Mg ha−1 for AD and 328, 656 Mg ha−1 for LS) and a single rate of conventional P fertilizer on leaching of PO4-P, and TKP were investigated in a hybrid poplar plantation in a coastal plain heavy mineral mine reclamation site. The effects of AD and LS biosolids aging on the transformations and losses of P applied with the biosolids were also studied. Zero tension lysimeters were installed at the site to collect leachate. Samples were collected at least monthly for 30 months between July 2006 and December 2008. We also analyzed biosolids P (labile P, Al-, Fe-bound-P, Ca-bound-P, total P, Mehlich 1 P) fractions. The loss of P was determined and P binding constituents were described via regression analysis. Orthophosphate and TKP from the DRI biosolids leached in negligible amounts, and were similar to leaching from conventional P fertilization. Most of the P was Al- and Fe-bound in the AD biosolids and Ca-bound in the LS biosolids. Labile P decreased with decrease in organic C, which indicated that P leaching potential from the DRI biosolids decreased with aging. Our results indicated that P mobility from biosolids of the type used should not pose a water quality risk. 相似文献
88.
Do Migrants Degrade Coastal Environments? Migration,Natural Resource Extraction and Poverty in North Sulawesi,Indonesia 总被引:1,自引:0,他引:1
Susan?CasselsEmail author Sara?R.?Curran Randall?Kramer 《Human ecology: an interdisciplinary journal》2005,33(3):329-363
Recent literature on migration and the environment has identified key mediating variables such as how migrants extract resources from the environment for their livelihoods, the rate and efficiency of extraction, and the social and economic context within which their extraction occurs. This paper investigates these variables in a new ecological setting using data from coastal fishing villages in North Sulawesi, Indonesia. We do not find as many differences between migrant and non-migrant families regarding destructive fishing behavior, technology, and investment as might have been expected from earlier theories. Instead, the context and timing of migrant assimilation seems to be more important in explaining apparent associations of migration and environmental impacts than simply migrants themselves. This finding fits well with recent literature in the field of international migration and immigrant incorporation. 相似文献
89.
The present study addresses the effects of oxygen exposure on the aerobic and anaerobic respiratory activity of Desulfovibrio desulfuricans strain DvO1. This strain was isolated from the highest sulfate-reduction positive most-probable-number dilution (10(6)) of an activated sludge sample, which had been subjected to 120 h of continuous aeration. Washed cell suspensions of strain DvO1 were aerated at 50% atmospheric oxygen saturation in sulfide-free media for a period of 33 h in the presence or absence of an external electron donor (10 mM lactate). During the aeration periods, samples were removed at intervals for determination of anaerobic INT [2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride]-reducing activity, anaerobic sulfate-reducing activity, and oxygen-reducing activity. The cell suspension aerated in the absence of lactate showed negligible endogenous oxygen reduction rates and therefore did not consume oxygen during the aeration period. In contrast, the cell suspension aerated in the presence of lactate sustained significant rates of oxygen reduction during the entire 33 h aeration period. Despite this, no explicit differences in the potential INT-, oxygen-, or sulfate-reducing activities were evident between the two cell suspensions during the aeration periods. Strain DvO1 remained viable throughout the 33 h aeration periods irrespective of the presence or absence of lactate, however, the oxygen exposure resulted in a dose-dependent reversible metabolic inactivation. Notably, lactate-dependent anaerobic sulfate-reducing activity recovered quickly upon anaerobiosis, and was more oxygen tolerant than lactate-dependent oxygen-reducing activity. 相似文献
90.
Jones DJ Jukes-Jones R Verschoyle RD Farmer PB Gescher A 《Bioorganic & medicinal chemistry》2005,13(24):6727-6731
To study the biological effects of quercetin, authentic products of quercetin metabolism are required as standards. The synthesis of quercetin sulfate standards is thus described. Quercetin was reacted with a 10-fold molar excess of sulfur trioxide-N-triethylamine, and the products were analyzed by HPLC and mass spectrometry. Four monosulfates and three disulfates were identified, and structural inferences were drawn by 1H NMR spectrometry of HPLC peak isolates. Analysis of the urine of rats that had received quercetin (1.9 g/kg po) yielded a single peak, which by comparison with the products of the reaction between quercetin and sulfur trioxide-N-triethylamine was identified as quercetin 3′-O-sulfate. 相似文献