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1.
The solubility advantage of indomethacin amorphized by co-grinding with Neusilin US2 in various media was investigated. Physical
mixtures of γ-indomethacin and Neusilin US2 (in the ratios 1:1, 1:4 and 1:5) were amorphized at room temperature employing
75% RH in a porcelain jar mill using zirconia balls. The crystallinity of the samples was determined using ATR-FTIR and PXRD.
The solubility and dissolution profiles of co-ground powders and crystalline counterparts were evaluated in 0.1 N HCl, water
and phosphate buffer (pH 6.8) in a USP type II dissolution apparatus at 250 rpm and 37 °C. Very high concentrations of dissolved
indomethacin as compared to the solubility of γ-indomethacin (~500 times in water and ~ 3.7 times in phosphate buffer) were
attained. However, the presence of other polymorphs detected by PXRD and a change in the pH of the medium made interpretation
of the results difficult. In 0.1 N HCl the solubility (i.e., the peak in a concentration versus time plot) of the amorphized drug in a 1:5 ratio with Neusilin increased to 109 times the solubility of crystalline γ-indomethacin
alone. An increase in amount of drug and Neusilin in the same ratio added to the dissolution medium also increased peak and
plateau dissolution concentrations. The presence of silicic acid and ions (Mg2+ and Al3+) in the dissolution media were found to cause the increase in the plateau concentration of indomethacin. Amorphization alone
does not account for all of the dissolution enhancement; acidity, ions, and silicic acid are major contributors to dissolution
enhancement. 相似文献
2.
Light-induced fluorescence (LIF) was evaluated as a process analytical technology to monitor blend homogeneity and establish
a relationship with high-performance liquid chromatography (HPLC). Secondary aims for this study included a determination
of blend steady-state, acceptable mixing time interval, and mixing end point. Also, identification of potential “dead spots”
in the 124 L intermediate bulk container mixing tote was explored. Individual samples from 13 sample locations were collected
at 0.25, 0.5, 0.75, 1, 2, 5, 10, and 20 min and analyzed using LIF and HPLC. LIF and HPLC methods showed similar mixing profiles.
A coefficient of determination (R
2) of 0.86 (p value < 0.0001) was obtained for a second-degree polynomial bivariate fit of LIF counts by HPLC percent label claim (%LC).
A significant linear relationship was determined between LIF percent relative standard (%RSD) and HPLC %RSD (R
2 = 0.97, p < 0.0001). The LIF steady-state, acceptable mixing time interval, and mixing end point were determined to be 1–20, 2–20,
and 2 min, respectively. The steady-state, acceptable mixing time interval, and mixing end point determined by HPLC were 1–20,
5–10, and 5 min, respectively. The Tukey–Kramer honestly significant difference analysis of HPLC %LC by sample location at
5 and 10 min mixing times showed that there was a statistical difference between the HPLC %LC group means at two blender locations. 相似文献
3.
The objective of the present investigation was to reduce the bitterness with improved dissolution, in acidic medium (pH 1.2),
of mefloquine hydrochloride (MFL). Microparticles were prepared by coacervation method using Eudragit E (EE) as polymer and
sodium hydroxide as precipitant. A 32 full factorial design was used for optimization wherein the drug concentration (A) and polymer concentration (B) were selected
as independent variables and the bitterness score, particle size and dissolution at various pH were selected as the dependent
variables. The desirability function approach has been employed in order to find the best compromise between the different
experimental responses. The model is further cross validated for bias. The optimized microparticles were characterized by
FT-IR, DSC, XRPD and SEM. Bitterness score was evaluated by human gustatory sensation test. Multiple linear regression analysis
revealed that the reduced bitterness of MFL can be obtained by controlling the dissolution of microparticles at pH 6.8 and
increasing the EE concentration. The increase in polymer concentration leads to reduction in dissolution of microparticles
at pH > 5 due to its insolubility. However the dissolution studies at pH 1.2 demonstrated enhanced dissolution of MFL from
microparticles might be due to the high porosity of the microparticles, hydrophilic nature of the EE, and improved wettability,
provided by the dissolved EE. The bitterness score of microparticles was decreased to zero compared to 3+ of pure ARM. In
conclusion the bitterness of MFL was reduced with improved dissolution at acidic pH. 相似文献
4.
In the sublingual (SL) cavity, compared with the gastrointestinal tract, tablets are subjected to minimal physiological agitation,
and a limited volume of saliva is available to facilitate disintegration and dissolution. None of the official compendial
dissolution apparatuses and methods simulate these SL conditions. In this study, a custom-made dissolution apparatus was constructed,
and a novel in vitro method that simulates SL conditions was evaluated. Several epinephrine 40 mg SL tablet formulations under development and
two commercial SL tablets, isosorbide dinitrate 5 mg and nitroglycerin 0.6 mg, were studied. The dissolution medium was 2 mL
of distilled water at 25°C. Dissolution was measured at 60 and 120 s. The novel in vitro method was validated for accuracy, reproducibility, and discrimination capability, and was compared with the official US
Pharmacopeia (USP) dissolution method using apparatus 2 (Paddle). The data obtained following the novel in vitro method were accurate and reproducible. This method was capable of detecting minor changes in SL formulations that could not
be detected using other in vitro tests. Results from the official USP dissolution method and our novel in vitro method were significantly different (p < 0.05). Results reflecting the dissolution of rapidly disintegrating tablets using simulated SL conditions were obtained
using the novel in vitro dissolution method. 相似文献
5.
A simple, high frequency, and reproducible method for plant regeneration through direct organogenesis from cotyledonary leaf
explants of Jatropha curcas was developed using Murashige and Skoog (MS) medium supplemented with different concentrations of thidiazuron (TDZ) or 6-benzyl
aminopurine (BAP). Medium containing TDZ has greater influence on regeneration as compared to BAP. The induced shoot buds
were transferred to MS medium containing 10 μM kinetin (Kn), 4.5 μM BAP, and 5.5 μM α-naphthaleneacetic acid (NAA) for shoot
proliferation. The proliferated shoots could be elongated on MS medium supplemented with different concentrations and combinations
of BAP, indole-3-acetic acid (IAA), NAA, and indole-3-butyric acid (IBA). MS medium with 2.25 μM BAP and 8.5 μM IAA was found
to be the best combination for shoot elongation. However, significant differences in plant regeneration and shoot elongation
were observed among the genotypes studied. Rooting was achieved when the basal cut end of elongated shoots were dipped in
half strength MS liquid medium containing different concentrations and combinations of IBA, IAA, and NAA for 4 days, followed
by transfer to growth regulators free half strength MS medium supplemented 0.25 mg l−1 activated charcoal. Elongated shoot treated with 15 μM IBA, 5.7 μM IAA, and 11 μM NAA resulted in highest percent rooting.
The rooted plants could be established in soil with more than 90% survival rate. The method developed may be useful in improvement
of J. curcas through genetic modification. 相似文献
6.
X. Ding B. Chou R.A. Graham S. Cheeti S. Percey L.C. Matassa S.A. Reuschel M. Meng S. Liu T. Voelker B.L. Lum P.J. Rudewicz C.E.C.A. Hop 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2010,878(9-10):785-790
To support clinical development, a solid phase extraction (SPE) liquid chromatographic-tandem mass spectrometry (LC-MS/MS) method for the determination of GDC-0449 concentrations in human plasma has been developed and validated. Samples (200 μl) were extracted using an Oasis MCX 10 mg 96-well SPE plate and the resulting extracts were analyzed using reverse-phase chromatography coupled with a turbo-ionspray interface. The method was validated over calibration curve range 5–5000 ng/mL. Quadratic regression and 1/x2 weighing were used. Within-run relative standard deviation (%RSD) was within 10.1% and accuracy ranged from 88.6% to 109.0% of nominal. Between-run %RSD was within 8.6% and accuracy ranged from 92.4% to 105.3% of nominal. Extraction recovery of GDC-0449 was between 88.3% and 91.2% as assessed using quality control sample concentrations. GDC-0449 was stable in plasma for 315 days when stored at ?70 °C and stable in reconstituted sample extracts for 117 h when stored at room temperature. Quantitative matrix effect/ion suppression experiment was performed and no significant matrix ion suppression was observed. This assay allows for the determination of GDC-0449 plasma concentrations over a sufficient time period to determine pharmacokinetic parameters at relevant clinical doses. 相似文献
7.
Shoot regeneration and occurrence of hyperhydricity in Aloe polyphylla were greatly affected by the type of gelling agent. The use of gelrite resulted in a significantly lower multiplication and
almost four times higher hyperhydricity (65%) compared to agar-solidified medium. Gelrite was further selected to evaluate
if hyperhydricity can be overcome by altering the physical properties of the gel, as represented by increasing gelrite concentrations.
Four concentrations of gelrite (0, 2.4, 6 and 16 g l−1) were tested in combination with zeatin, N6-benzyladenine (BA) or thidiazuron (TDZ). Almost all explants grown in liquid media in the presence of cytokinins became hyperhydric
and lost their ability to regenerate. The greatest shoot formation was obtained on media with 2.4 g l−1 gelrite and 5 μM zeatin or BA, however hyperhydricity was very high. Satisfactory reduction in hyperhydricity was achieved
only at 16 g l−1 gelrite, under which conditions the multiplication also decreased. The use of TDZ resulted in very low shoot regeneration
and high hyperhydricity irrespective of the gelrite concentration. 相似文献
8.
Chung CM Cho KW Kim YJ Yamamoto K Chung TH 《Bioprocess and biosystems engineering》2012,35(4):503-511
A modified ludzack ettinger reactor (MLE) combined with a post-denitrification reactor (PDMLE) using electroflotation (EF)
as a secondary clarifier was investigated on its feasibility and process performance. Results indicated that higher mixed
liquor suspended solids (MLSS) concentrations in bioreactor (5,350 ± 352 mg L−1) were maintained via the highly concentrated return sludge (16,771 ± 991 mg L−1) from the EF clarifier and the effluent suspended solids (SS) concentrations continued relatively low, representing effluent
SS concentration of 1.71 ± 1.16 mg L−1, compared with GS-A2O process during the operation of four months. The denitrification was improved by combining MLE process
with post-denitrification based on endogenous decay (i.e. no additional carbon source was added), resulting in the removal
efficiencies of TN were about 91 and 59% for the influent C/N ratio of 10 and 5, respectively, revealing relatively high nitrogen
removal as compared with EF-A2O and gravity settling (GS)-A2O processes as a control. The nitrogen balance analysis indicates
that pre-denitrification and post-denitrification contributed to 78 and 22% of TN removed, respectively. 相似文献
9.
Margarita Elena Rentería-Cano Laura Sánchez-Velasco Evgueni Shumilin Miguel F. Lavín Jaime Gómez-Gutiérrez 《Biological trace element research》2011,142(3):848-864
We report the distribution of major and trace element concentrations in epipelagic zooplankton collected in the Northern Gulf
of California in August 2003. The Bray–Curtis index defined three element assemblages in zooplankton: (1) major metals, which
included only two elements, Na (3.6–17.0%) and Ca (1.0–4.8%). Na had its highest concentrations in the shallow tidally mixed
Upper Gulf, where high salinity, temperature, and zooplankton biomass (dominated by copepods) prevailed. Ca showed its highest
concentrations south of Ballenas Channel, characterized by tidal mixing and convergence-induced upwelling, indicated by low
sea-surface temperature, salinity, and zooplankton biomass; (2) Six biological essential elements, like Fe (80–9,100 mg kg−1) and Zn (20–2,570 mg kg−1), were detected in high concentrations in zooplankton collected near Guaymas Basin, which had high surface temperature and
chlorophyll a concentrations. (3) Metals of terrigenous origin, such as Sc (0.01–1.4 mg kg−1) and Th (0.03–2.3 mg kg−1), and redox-sensitive metals, like Co (3–23.8 mg kg−1); this was the assemblage with the largest number of elements (15). Both types of elements of assemblage 3 had maximum concentrations
in the cyclonic eddy that dominates the summer circulation in the Northern region. We concluded that sediment resuspension
by tidal mixing in the Upper Gulf, upwelling south of Ballenas Channel, and the cyclonic eddy were key oceanographic features
that affected the element concentrations of epipelagic zooplankton in the Northern Gulf of California. Oceanographic mechanisms
such as these may contribute to element incorporation in marine organisms in other seas. 相似文献
10.
Forming a salt is a common way to increase the solubility of a poorly soluble compound. However, the solubility enhancement
gained by salt formation may be lost due to solution-mediated phase transformation (SMPT) during dissolution. The SMPT of
a salt can occur due to a supersaturated solution near the dissolving surface caused by pH or other solution conditions. In
addition to changes in pH, surfactants are also known to affect SMPT. In this study, SMPT of a highly soluble salt, haloperidol
mesylate, at pH 7 in the presence of a commonly used surfactant, sodium lauryl sulfate (SLS), was investigated. Dissolution
experiments were performed using a flow-through dissolution apparatus with solutions containing various concentrations of
SLS. Compacts of haloperidol mesylate were observed during dissolution in the flow-through apparatus using a stereomicroscope.
Raman microscopy was used to characterize solids. The dissolution of haloperidol mesylate was significantly influenced by
the addition of sodium lauryl sulfate. In conditions where SMPT was expected, the addition of SLS at low concentrations (0.1–0.2 mM)
reduced the dissolution of haloperidol mesylate. In solutions containing concentrations of SLS above the critical micelle
concentration (CMC) (10–15 mM), the dissolution of haloperidol mesylate increased compared to below the CMC. The solids recovered
from solubility experiments of haloperidol mesylate indicated that haloperidol free base precipitated at all concentrations
of SLS. Above 5 mM of SLS, Raman microscopy suggested a new form, perhaps the estolate salt. The addition of surfactant in
solids that undergo solution-mediated phase transformation can add complexity to the dissolution profiles and conversion. 相似文献
11.
We compared phytoplankton and phytobenthos pigment strategies in 17 shallow lakes and ponds from northern Canada and Alaska,
sampled during mid to late summer. Benthic chlorophyll a concentrations (8–261 mg m−2) greatly exceeded those of the phytoplankton (0.008–1.4 mg m−2) in all sites. Cyanobacteria dominated the phytobenthos, while green algae and fucoxanthin-groups characterized the plankton.
Both communities had higher photoprotection in cold, UV-transparent, high latitude waters. Phytoplankton had higher concentrations
of photoprotective carotenoids per unit chlorophyll a than the phytobenthos. The planktonic photoprotective pigments were positively correlated with UV-penetration, and inversely
correlated with temperature and coloured dissolved organic matter. A partial redundancy analysis showed that the benthic pigments
were related to latitude, area and temperature. The UV-screening compound scytonemin occurred in high concentrations in the
phytobenthos and was inversely related to temperature, while benthic carotenoids per unit chlorophyll a showed much lower variability among sites. These differing pigment strategies imply divergent responses to environmental
change between the phytobenthos and phytoplankton in high latitude lakes. 相似文献
12.
Deniz Özkan Deniz Yüzbaşıoğlu Fatma Ünal Serkan Yılmaz Hüseyin Aksoy 《Cytotechnology》2009,59(2):73-80
The organophosphorous insecticide acephate was tested for its ability to induce in vitro cytogenetic effect in human peripheral
lymphocytes by using the chromosomal aberrations (CAs), sister chromatid exchange (SCE) and micronuclei (MN) assay. The level
of nuclear DNA damage of acephate was evaluated by using the comet assay. Concentrations of 12.5, 25, 50, 100 and 200 μg mL−1 of acephate were used. All concentrations of acephate induced significant increase in the frequency of CAs and in the formation
of MN dose dependently (r = 0.92 at 24 h, r = 0.95 at 48 h for CAs, r = 0.87 for MN). A significant increase was observed in induction of SCE at 50, 100 and 200 μg mL−1 concentrations during 24 h treatment and at all concentrations (except 12.5 μg mL−1) during 48 h treatment period in a dose-dependent manner (r = 0.84 at 24 h, r = 0.88 at 48 h). Acephate did not affect the replicative index and cytokinesis-block proliferation index (CBPI). However,
it significantly decreased the mitotic index at all three highest concentrations (50, 100, 200 μg mL−1) for 24 h treatment and at all concentrations (except 12.5 μg mL−1) for 48 h treatment, dose-dependently (r = 0.94 at 24 h, r = 0.92 at 48 h). A significant increase in mean comet tail length was observed at 100 and 200 μg mL−1 concentrations compared with negative control in a concentration-dependent manner (r = 0.94). The mean comet tail intensity was significantly increased at only 200 μg mL−1 concentration. The present results indicate that acephate is a clastogenic, cytotoxic agent and it causes DNA damage at high
concentrations in human lymphocytes in culture. 相似文献
13.
Yuanhao Wang Hu Teng Zhilong Xiu 《Journal of industrial microbiology & biotechnology》2011,38(6):705-715
The microbial production of 1,3-propaneidol (1,3-PD) by Klebsiella pneumoniae in continuous fermentation was investigated under low, medium and high glycerol concentrations in the absence and presence
of oxygen. The production of 1,3-PD increased with increasing glycerol concentrations, reaching a maximum (266 mmol l−1) under high glycerol concentration (760 mmol l−1) with air sparging at 0.04 vvm. The yield of 1,3-PD, however, decreased gradually with increasing glycerol concentrations,
with the highest yield (0.52 mol mol−1) obtained for low glycerol concentration (270 mmol l−1) under anaerobic condition. Enzyme activity assays showed that the specific activity of glycerol dehydratase was highest
(0.04 U mg−1) for culture sparged with 0.04 vvm air under high glycerol concentration. The specific activities of glycerol dehydrogenase
and 1,3-propanediol oxidoreductase were also improved for all glycerol concentrations and in the presence of oxygen, implying
that the dha operon was not repressed under microaerobic conditions. Analysis of metabolic fluxes showed that more carbon flux was shifted
to the oxidative pathway with increasing glycerol concentrations, resulting in a reduced flux to 1,3-PD formation. However,
the increases in carbon fluxes were not evenly distributed among the oxidative branches of the pathway. Furthermore, ethanol
and acetic acid levels were slightly increased whereas 2,3-butanediol and lactic levels were greatly enhanced. 相似文献
14.
Ö. Şimşek N. Akkoç A. H. Çon F. Özçelik P. E. J. Saris Mustafa Akçelik 《Journal of industrial microbiology & biotechnology》2009,36(6):863-871
Nisin production in continuous cultures of bioengineered Lactococcus lactis strains that incorporate additional immunity and regulation genes was studied. Highest nisin activities were observed at
0.2 h–1 dilution rate and 12.5 g l–1 fructose concentration for all strains. Recombinant strains were able to produce greater amounts of nisin at dilution rates
below 0.3 h−1 compared to the control strain. However, this significant difference disappeared at dilution rates of 0.4 and 0.5 h–1. For the strains LL27, LAC338, LAC339, and LAC340, optimum conditions for nisin production were determined to be at 0.29,
0.26, 0.27, and 0.27 h–1 dilution rates and 11.95, 12.01, 11.63, and 12.50 g l–1 fructose concentrations, respectively. The highest nisin productivity, 496 IU ml–1 h–1, was achieved with LAC339. The results of this study suggest that low dilution rates stabilize the high specific nisin productivity
of the bioengineered strains in continuous fermentation. Moreover, response surface methodology analysis showed that regulation
genes yielded high nisin productivity at wide ranges of dilution rates and fructose concentrations. 相似文献
15.
Shinawar Waseem Ali Rong Li Wei-you Zhou Ji-quan Sun Peng Guo Ji-ping Ma Shun-peng Li 《Biodegradation》2010,21(3):441-452
Abamectin is widely used in agriculture as an insecticide and in veterinary as an anti-parasitic agent, and has caused great
environmental pollution by posing potential risk to non-target soil invertebrates and nearby aquatic systems. A bacterium
designated GB-01, which was capable of degrading abamectin, was isolated from soil by enrichment culture method. On the basis
of morphological, physiological and biochemical characteristics, combined with phylogenetic analysis of 16S rRNA gene, the
bacterium GB-01 was identified as Burkholderia cepacia-like species. The bacterium GB-01 was able to utilize abamectin as its sole carbon source for growth, and could degrade more
than 90% of abamectin at initial concentrations of 50 and 100 mg l−1 in mineral salt medium in 30 and 36 h, respectively. The longer degradation cycle was observed with abamectin concentrations
higher than 100 mg l−1. Optimal growth temperatures and pH values with highest degradation rate were 30–35°C and 7–8, respectively. Two new degradation
products were identified and characterized by high performance liquid chromatography-tandem mass spectrometry (HPLC–MS/MS)
based mass spectral data and a plausible partial degradation pathway of abamectin was proposed. This is the first report in
which an abamectin-degrading Burkholderia species isolated from soil was identified and characterized. 相似文献
16.
Sharon B. Velasquez-Orta Ian M. Head Thomas P. Curtis Keith Scott Jonathan R. Lloyd Harald von Canstein 《Applied microbiology and biotechnology》2010,85(5):1373-1381
The effect of electron shuttles on electron transfer to microbial fuel cell (MFC) anodes was studied in systems where direct
contact with the anode was precluded. MFCs were inoculated with Shewanella cells, and flavins used as the electron shuttling compound. In MFCs with no added electron shuttles, flavin concentrations
monitored in the MFCs' bulk liquid increased continuously with FMN as the predominant flavin. The maximum concentrations were
0.6 μM for flavin mononucleotide and 0.2 μM for riboflavin. In MFCs with added flavins, micro-molar concentrations were shown
to increase current and power output. The peak current was at least four times higher in MFCs with high concentrations of
flavins (4.5–5.5 μM) than in MFCs with low concentrations (0.2–0.6 μM). Although high power outputs (around 150 mW/m2) were achieved in MFCs with high concentrations of flavins, a Clostridium-like bacterium along with other reactor limitations affected overall coulombic efficiencies (CE) obtained, achieving a maximum
CE of 13%. Electron shuttle compounds (flavins) permitted bacteria to utilise a remote electron acceptor (anode) that was
not accessible to the cells allowing current production until the electron donor (lactate) was consumed. 相似文献
17.
L. Charpy M. Rodier A. Couté C. Perrette-Gallet C. Bley-Loëz 《Coral reefs (Online)》2010,29(3):771-783
Closure of the Clipperton Island atoll (10°17′ N 109°13′ W), now a meromictic lake, is estimated to have occurred between
1839 and 1849. It was still closed in 2005. Brackish waters in the upper layer (0–10 m) were oxygenated, while saline waters
in the deep layer (>20 m) were anoxic. Allowing for the methodological difficulties of earlier measurements, the physical
characteristics of the lagoon did not seem to have changed significantly since the last expedition (1980). The intermediate
layer between brackish and saline waters was characterized by a strong density gradient and a temperature inversion of up
to 1.6°C. Microbial activity, water exchange between the deep layer and surrounding oceanic waters and the geothermal flux
hypothesis are discussed. The low DIN and SRP concentrations observed in the upper layer, despite high nutrient input by seabird
droppings, reflect the high nutrient uptake by primary producers as attested by the elevated overall gross primary production
(6.6 g C m−2 day−1), and high suspended photosynthetic biomass (2.23 ± 0.23 μg Chl a l−1) and production (263 ± 27 μg C l−1 day−1). Phytoplankton composition changed in 67 years with the advent of new taxa and the disappearance of previously recorded
species. The freshwater phytoplanktonic community comprised 43 taxa: 37 newly identified during the expedition and 6 previously
noted; 16 species previously found were not seen in 2005. The closure of the lagoon, combined with the positive precipitation–evaporation
budget characteristic of the region, has induced drastic changes in lagoon functioning compared with other closed atolls. 相似文献
18.
Permissible Value for Vanadium in Allitic Udic Ferrisols Based on Physiological Responses of Green Chinese Cabbage and Soil Microbes 总被引:2,自引:0,他引:2
Greenhouse experiments were conducted to study the permissible value of vanadium (V) based on the growth and physiological
responses of green Chinese cabbage (Brassica chinensis L.), and effects of V on microbial biomass carbon (MBC) and enzyme activities in allitic udic ferrisols were also studied.
The results showed that biomass of cabbage grown on soil treated with 133 mg V kg−1 significantly decreased by 25.1% compared with the control (P < 0.05). Vanadium concentrations in leaves and roots increased with increasing soil V concentration. Contents of vitamin
C (Vc) increased by 10.3%, while that of soluble sugar in leaves significantly decreased by 54.0% when soil V concentration
was 133 mg kg−1, respectively. The uptake of essential nutrient elements by cabbage was disturbed when soil V concentration exceeded 253 mg kg−1. Soil MBC was significantly stimulated by 15.5%, while dehydrogenase activity significantly decreased by 62.8% and urease
activity slightly changed at treatment of 133 mg V kg−1 as compared with the control, respectively. Therefore, the permissible value of V in allitic udic ferrisols is proposed as
130 mg kg−1. 相似文献
19.
Phenol is one of the major toxic pollutants in the wastes generated by a number of industries and needs to be eliminated before
their discharge. Although microbial degradation is a preferred method of waste treatment for phenol removal, the general inability
of the degrading strains to tolerate higher substrate concentrations has been a bottleneck. Immobilization of the microorganism
in suitable matrices has been shown to circumvent this problem to some extent. In this study, cells of Pseudomonas sp. CP4, a laboratory isolate that degrades phenol, cresols, and other aromatics, were immobilized by entrapment in Ca-alginate
and agar gel beads, separately and their performance in a fluidized bed bioreactor was compared. In batch runs, with an aeration
rate of 1 vol−1 vol−1 min−1, at 30°C and pH 7.0 ± 0.2, agar-encapsulated cells degraded up to 3000 mg l−1 of phenol as compared to 1500 mg l−1 by Ca-alginate-entrapped cells whereas free cells could tolerate only 1000 mg l−1. In a continuous process with Ca-alginate entrapped cells a degradation rate of 200 mg phenol l−1 h−1 was obtained while agar-entrapped cells were far superior and could withstand and degrade up to 4000 mg phenol l−1 in the feed with a maximum degradation rate of 400 mg phenol l−1 h−1. The results indicate a clear possibility of development of an efficient treatment technology for phenol containing waste
waters with the agar-entrapped bacterial strain, Pseudomonas sp. CP4. 相似文献
20.
Xiuyun Cao Chunlei Song Yiyong Zhou Alena Štrojsová Petr Znachor Eliška Zapomělová Jaroslav Vrba 《Limnology》2009,10(2):95-104
Extracellular phosphatases are an important part of the phosphorus cycle in aquatic environments. Phosphatase activity (PA)
in plankton was studied in seven subtropical shallow lakes of different exploitation management and trophic status in the
urban area of Wuhan City. Bulk PA was rather high (range 1.1–11 μmol l−1 h−1), although concentrations of soluble reactive phosphorus (SRP) were also high (range 27 μg P l−1 to ~1.5 mg P l−1) in all lakes. Cell-associated extracellular PA in phytoplankton was detected using the fluorescence-labelled enzyme activity
technique. Phytoplankton species partly contributed to the bulk PA. We found explicit differences in the presence of cell-associated
phosphatase within the main phytoplankton groups; species belonging to Chlorophyta and Dinophyta were regularly phosphatase-positive,
while Cyanophyta and Bacillariophyceae were phosphatase-negative in all but one case. Furthermore, there is a certain potential
of extracellular phosphatases produced by heterotrophic nanoflagellates in most of the lakes. This new finding compromises
the ‘traditional’ interpretation of bulk phosphatase data as being due to overall phytoplankton or bacterial P regeneration. 相似文献