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1.
Zamora-Castro J Paniagua-Michel J Lezama-Cervantes C 《Marine biotechnology (New York, N.Y.)》2008,10(2):181-189
A novel alternative for wastewater effluent bioremediation was developed using constructed microbial mats on low-density polyester.
This biotechnology showed high removal efficiencies for nitrogen and phosphorous in a short retention time (48 h): 94% for
orthophosphate (7.78 g m3 d−1), 79% for ammonium (11.30 g m−3 d−1), 78% for nitrite (7.46 g m−3 d−1), and 83% for nitrate (8.55 g m−3 d−1). The microbial mats were dominated by Cyanobacteria genera such as Chroococcus sp., Lyngbya sp., and bacteria of the subclass Proteobacteria representative of the Eubacteria Domain. Nitzschia sp. was the dominant Eukaryote Domain. Various N and P substrates in the wastewater permit the growth of self-forming and
self-sustaining bacterial, microalgal, and cyanobacterial communities on a polyester support. The result is the continuous,
self-sufficient growth of microbial mats. This is an innovative, economical, and environmentally safe alternative for the
treatment of wastewater effluents in coastal marine environments. 相似文献
2.
Fluctuating hydrochemistry, as a result of extreme hydrological regimes, imposes major physiological constraints on the biota
of ephemeral saline lakes. While the inverse relationship between salinity and zooplankton species richness is well-known
across salinity gradients, few studies have documented closely the response of zooplankton to seasonal changes in salinity.
Weekly sampling during two flood seasons at Sua Pan, an intermittent saline lake in central Botswana demonstrated the importance
of spatial and temporal salinity gradients for crustacean community composition, associated with a decline in species richness,
from 11 to three species. Conductivity ranged between 320 and 125,800 μS cm−1 during seasonal flooding; changing from dominance by
and , Ca2+ and Mg2+, at the beginning of the floods, to NaCl dominated waters as the lake dried out and salinities increased. pH estimates generally
ranged between 8.6 and 10, with maximum values recorded during initial flooding. Crustaceans comprised mainly Branchinella spinosa, Moina belli, Lovenula africana and Limnocythere tudoranceai, all of which occurred across a wide range of salinities, while halotolerant freshwater species (Metadiaptomus transvaalensis, Leptestheria striatochonca and the ostracods Plesiocypridopsis aldabrae, Cypridopsis newtoni and a newly identified Potamocypris species) disappeared above conductivities of 1,500 μS cm−1. A unique crustacean composition in southern Africa was attributed to Sua Pans’ rare chemical composition among southern
African saline lakes; flood waters on Sua Pan contained a higher proportion of Na+ and , and less K+, Mg2+ and than over 80% of records from salt pans elsewhere in southern African. The freshwater species of crustaceans in Sua Pan were
similar to those found in other southern Africa lakes, and these similarities decreased in lakes with higher pH and proportions
of Na, and less SO4 and Mg in their chemical composition. The predominant saline tolerant species on Sua Pan, however, showed a greater similarity
to those in saline lakes in southern and East Africa with higher proportions of and, particularly, Mg2+ in their chemical composition.
Handling editor: J. M. Melack 相似文献
3.
Yun Hee Kang Jong Ahm Shin Myung Sook Kim Ik Kyo Chung 《Journal of applied phycology》2008,20(2):183-190
In integrated multi-trophic aquaculture (IMTA), seaweeds have the capacity to reduce the environmental impact of nitrogen-rich
effluents in coastal ecosystems. To establish such bioremediation systems, selection of suitable seaweed species is important.
The distribution and productivity of seaweeds vary seasonally based on water temperature and photoperiod. In Korea, candidate
genera such as Pophyra, Laminaria, and Undaria grow from autumn to spring. In contrast, Codium grows well at relatively high water temperatures in summer. Thus, aquaculture systems potentially could capitalize on Codium’s capacity for rapid growth in the warm temperatures of late summer and early fall. In this study, we investigated ammonium
uptake and removal efficiency by Codium fragile. In laboratory experiments, we grew C. fragile under various water temperatures (10, 15, 20, and 25°C), irradiances (dark, 10, and 100 μmol photons m−2 s−1), and initial ammonium concentrations (150 and 300 μM); in all cases, C. fragile exhausted the ammonium supply for 6 h. At 150 μM of , ammonium removal efficiency was greatest (99.5 ± 2.6%) when C. fragile was incubated at 20°C under 100 μmol photons m−2 s−1. At 300 μM of , removal efficiency was greatest (86.3 ± 2.1%) at 25°C under 100 μmol photons m−2 s−1. Ammonium removal efficiency was significantly greater at 20 and 25°C under irradiance of 100 μmol photons m−2 s−1 than under other conditions tested. 相似文献
4.
Phytoplankton dynamics,primary productivity and community metabolism in a north-central Texas pond 总被引:2,自引:2,他引:0
Phytoplankton diversity, primary productivity and community metabolism were measured for 1 year in a 0.94 ha pond located
in north-central Texas. Gross primary production ranged from 4.5 to 46.8 kcal m−2 day−1 (
=22.0 kcal m−2 day−1) and community metabolism ranged from 7.3 to 32.4 kcal m−2 day−1 (
=14.8 kcal m−2 day−1). Average production/respiration ratio (1.5) showed that the pond was principally autotrophic. Photosynthetic efficiency
(gross primary production/0.5 total solar radiation) ranged from 0.32 to 2.8 with a mean of 1.2. Phytoplankton diversity based
on numbers and biomass fluctuated greatly. Highest gross primary productivity occurred during Cyanophyta blooms in late summer-early
fall when species diversity was minimal. Water temperature and turbidity, which governed light penetration, were the principal
determinants of primary production. 相似文献
5.
Leaching losses of inorganic N and DOC following repeated drying and wetting of a spruce forest soil
Forest soils are frequently subjected to dry–wet cycles, but little is known about the effects of repeated drying and wetting
and wetting intensity on fluxes of , and DOC. Here, undisturbed soil columns consisting of organic horizons (O columns) and organic horizons plus mineral soil
(O + M columns) from a mature Norway spruce stand at the Fichtelgebirge; Germany, were repeatedly desiccated and subsequently
wetted by applying different amounts of water (8, 20 and 50 mm day−1) during the initial wetting phase. The constantly moist controls were not desiccated and received 4 mm day−1 during the entire wetting periods. Cumulative inorganic N fluxes of the control were 12.4 g N m−2 (O columns) and 11.4 g N m−2 (O + M columns) over 225 days. Repeated drying and wetting reduced cumulative and fluxes of the O columns by 47–60 and 76–85%, respectively. Increasing (0.6–1.1 g N m−2) and decreasing fluxes (7.6–9.6 g N m−2) indicate a reduction in net nitrification in the O + M columns. The negative effect of dry–wet cycles was attributed to
reduced net N mineralisation during both the desiccation and wetting periods. The soils subjected to dry–wet cycles were considerably
drier at the final wetting period, suggesting that hydrophobicity of soil organic matter may persist for weeks or even months.
Based on results from this study and from the literature we hypothesise that N mineralisation is mostly constrained by hydrophobicity
in spruce forests during the growing season. Wetting intensity did mostly not alter N and DOC concentrations and fluxes. Mean
DOC concentrations increased by the treatment from 45 mg l−1 to 61–77 mg l−1 in the O tlsbba columns and from 12 mg l−1 to 21–25 mg l−1 in the O + M columns. Spectroscopic properties of DOC from the O columns markedly differed within each wetting period, pointing
to enhanced release of rather easily decomposable substrates in the initial wetting phases and the release of more hardly
decomposable substrates in the final wetting phases. Our results suggest a small additional DOC input from organic horizons
to the mineral soil owing to drying and wetting. 相似文献
6.
Soil Respiration in European Grasslands in Relation to Climate and Assimilate Supply 总被引:9,自引:0,他引:9
Michael Bahn Mirco Rodeghiero Margaret Anderson-Dunn Sabina Dore Cristina Gimeno Matthias Drösler Michael Williams Christof Ammann Frank Berninger Chris Flechard Stephanie Jones Manuela Balzarolo Suresh Kumar Christian Newesely Tibor Priwitzer Antonio Raschi Rolf Siegwolf Sanna Susiluoto John Tenhunen Georg Wohlfahrt Alexander Cernusca 《Ecosystems》2008,11(8):1352-1367
Soil respiration constitutes the second largest flux of carbon (C) between terrestrial ecosystems and the atmosphere. This
study provides a synthesis of soil respiration (R
s) in 20 European grasslands across a climatic transect, including ten meadows, eight pastures and two unmanaged grasslands.
Maximum rates of R
s (
), R
s at a reference soil temperature (10°C; ) and annual R
s (estimated for 13 sites) ranged from 1.9 to 15.9 μmol CO2 m−2 s−1, 0.3 to 5.5 μmol CO2 m−2 s−1 and 58 to 1988 g C m−2 y−1, respectively. Values obtained for Central European mountain meadows are amongst the highest so far reported for any type
of ecosystem. Across all sites was closely related to . Assimilate supply affected R
s at timescales from daily (but not necessarily diurnal) to annual. Reductions of assimilate supply by removal of aboveground
biomass through grazing and cutting resulted in a rapid and a significant decrease of R
s. Temperature-independent seasonal fluctuations of R
s of an intensively managed pasture were closely related to changes in leaf area index (LAI). Across sites increased with mean annual soil temperature (MAT), LAI and gross primary productivity (GPP), indicating that assimilate supply
overrides potential acclimation to prevailing temperatures. Also annual R
s was closely related to LAI and GPP. Because the latter two parameters were coupled to MAT, temperature was a suitable surrogate
for deriving estimates of annual R
s across the grasslands studied. These findings contribute to our understanding of regional patterns of soil C fluxes and highlight
the importance of assimilate supply for soil CO2 emissions at various timescales. 相似文献
7.
Can biological nitrification inhibition (BNI) genes from perennial Leymus racemosus (Triticeae) combat nitrification in wheat farming? 总被引:1,自引:0,他引:1
G. V. Subbarao Ban Tomohiro Kishii Masahiro Ito Osamu H. Samejima H. Y. Wang S. J. Pearse S. Gopalakrishnan K. Nakahara A. K. M. Zakir Hossain H. Tsujimoto W. L. Berry 《Plant and Soil》2007,299(1-2):55-64
Using a recombinant luminescent Nitrosomonas europaea assay to quantify biological nitrification inhibition (BNI), we found that a wild relative of wheat (Leymus racemosus (Lam.) Tzvelev) had a high BNI capacity and releases about 20 times more BNI compounds (about 30 ATU g−1 root dry weight 24 h−1) than Triticum aestivum L. (cultivated wheat). The root exudate from cultivated wheat has no inhibitory effect on nitrification when applied to soil;
however, the root exudate from L. racemous suppressed formation and kept more than 90% of the soil’s inorganic-N in the -form for 60 days. The high-BNI capacity of L. racemosus is mostly associated with chromosome Lr#n. Two other chromosomes Lr#J, and Lr#I also have an influence on BNI production.
Tolerance of L. racemosus to is controlled by chromosome 7Lr#1-1. Sustained release of BNI compounds occurred only in the presence of in the root environment. Given the level of BNI production expressed in DALr#n and assuming normal plant growth, we estimated
that nearly 87,500,000 ATU of BNI activity ha−1 day−1 could be released in a field of vigorously growing wheat; this amounts to the equivalent of the inhibitory effect from the
application of 52.5 g of the synthetic nitrification inhibitor nitrapyrin (one AT unit of BNI activity is equivalent to 0.6 μg
of nitrapyrin). At this rate of BNI production it would take only 19 days for a BNI-enabled wheat crop to produce the inhibitory
power of a standard commercial application of nitrapyrin, 1 kg ha−1. The synthetic nitrification inhibitor, dicyandiamide, blocked specifically the AMO (ammonia monooxygenase) pathway, while
the BNI from L. racemosus blocked the HAO (hydroxylamine oxidoreductase) pathway in Nitrosomonas. Here we report the first finding of high production of BNI in a wild relative of any cereal and its successful introduction
and expression in cultivated wheat. These results demonstrate the potential for empowering the new generation of wheat cultivars
with high-BNI capacity to control nitrification in wheat-production systems.
Responsible Editor: Hans Lambers. 相似文献
8.
Genetically engineered pacemaking in ventricular cells has been achieved by down-regulation of the time independent inward rectifying current (I
K1), or insertion of the hyperpolarisation-activated funny current (I
f). We analyse the membrane system (i.e. ionic concentrations clamped) of an epicardial Luo-Rudy dynamic cell model using continuation algorithms with the maximum conductance () of I
K1 and I
f as bifurcation parameters. Pacemaker activity can be induced either via Hopf or homoclinic bifurcations. As
K1 is decreased by ≈74%, autorhythmicity emerged via a homoclinic bifurcation, i.e., the periodicity first appear with infinitely large periods. In contrast, the insertion of
f induced periodicity via a subcritical Hopf bifurcation at
f≈ 0.25 mSμF−1. Stable autorhythmic action potentials occurred at
f > 0.329 mSμF−1. 相似文献
9.
Seasonality and controls of phytoplankton productivity in the middle Cape Fear River, USA 总被引:1,自引:0,他引:1
Our 1 year study was aimed at assessing seasonal patterns and controls on phytoplankton primary production (PPR) and biomass
(chlorophyll a) in a fourth order section of the middle Cape Fear River in North Carolina, USA, and to determine the impact of three low-head
lock and dam (LD) structures on these variables within the 70 km study reach of this coastal river. Mean concentrations of
NO3
−–N, NH4
+–N and soluble reactive phosphorus (SRP) averaged 52.9, 6.0, and 3.6 μmol l−1 in monthly sampling, while the average light attenuation coefficient was 2.4 m−1. The average euphotic depth was 2.1 m. Nutrient concentrations and attenuation coefficients were not significantly different
above versus below each LD, or along the entire study reach. Significantly higher concentrations of dissolved O2 below versus above each LD were attributed to re-aeration during spillway transit. No seasonal pattern in physicochemical
properties was apparent. Phytoplankton chlorophyll a concentrations ranged from <1 to 36 μg l−1, while rates of primary production ranged from 18 to 2,580 mg C m−2 day−1, with values for both variables peaking in the spring and early summer. Chlorophyll a and primary productivity values were consistently higher above versus below each LD in May and June suggesting a seasonal
effect, but values were otherwise similar such that overall means were not significantly different. Several factors point
to light as the primary control on phytoplankton in the middle Cape Fear River: high nutrient concentrations; a low ratio
of euphotic : mixing depth (0.46); progressive increases in chlorophyll a and radiocarbon uptake in all treatments in quarterly nutrient enrichment bioassays conducted at levels of irradiance elevated
relative to in situ river values; and consistently low quarterly values of
(maximum rate of chlorophyll-normalized C uptake; ≤3.7 mg C mg chl a−1 h−1) and I
k (light saturation parameter; ≤104 μmol photons m−2 s−1) for photosynthetic light–response (P–I) curves.
Handling editor: L. Naselli-Flores 相似文献
10.
Factors affecting denitrification in agricultural headwater streams in Northeast Ohio,USA 总被引:2,自引:0,他引:2
As a result of increased anthropogenic nitrogen (N) loading in surface waters of agricultural watersheds, there is enhanced
interest to understand and quantify N removal mechanisms. Denitrification, an important N removal mechanism in aquatic systems,
may contribute to reducing N pollution in agricultural headwater streams. However, the key factors controlling this process
in lotic systems remain unclear. The objective of our study was to examine the factors regulating rates of denitrification
in the sediments of agricultural headwater streams in the mid-western USA. Denitrification rates were variable among streams
and treatments (<0.1–28.0 μg N g AFDM−1 h−1) and on average, were higher than those reported for similar headwater streams. Carbon quantity and quality, and pH had no
effect on denitrification, while temperature and nitrate (
) concentrations had a positive effect on rates of denitrification. Specifically, controlled denitrification following Michaelis-Menten kinetics. We calculated a value of km (1.0 mg -N L-1) that was comparable to other studies in aquatic sediments but was well below the median in-stream concentrations (5.2–17.4 mg -N L−1) observed at the study sites. Despite high rates of denitrification, this removal mechanism is most likely saturated in the agricultural headwater streams we examined, suggesting that these systems are not effective at removing
in-stream N.
Handling editor: D. Ryder 相似文献
11.
Algal communities inhabiting four calamine mine spoils differing in time since cessation of exploitation and loaded with high
concentrations of zinc (20,284–61,599 μg g−1 soil DW), lead (2,620–3,885 μg g−1 DW) and cadmium (104–232 μg g−1 DW) were studied. In dump soils of slightly alkaline pH (7.28–7.52) and low nutrient (, , ) concentrations, chlorophyll a content ranged from 0.41 to 2.27 μg g−1 soil DW. In total, 23 algal species were recorded. Chlorophyta were the dominant taxonomic group (42–55% of all identified
species) followed by Cyanobacteria (28–36%) and Heterokontophyta (13–21%). The highest species richness (18) was observed
in the oldest dump (120 years old) with natural succession, while in younger dumps it was lower (11–15). Total algal abundance
ranged between 5.5 and 19.1 × 102 ind. g−1 soil DW, and values of Margalef’s diversity indices (1.59–2.25) were low. These results may suggest that both high concentrations
of heavy metals and low nutrient content influenced the algal communities in all the dumps studied. The differences in algal
microflora observed between tailing dumps may indicate that habitat quality improved with time and that algae isolated from
Zn/Pb-loaded soils may be Zn/Pb-resistant ecotypes of ubiquitous species. 相似文献
12.
Gonzales AL Lee W Spencer SR Oropeza RA Chapman JV Ku JY Eskandari S 《The Journal of membrane biology》2007,220(1-3):33-51
We combined electrophysiological and freeze-fracture methods to estimate the unitary turnover rate of the γ-aminobutyric acid
(GABA) transporter GAT1. Human GAT1 was expressed in Xenopus laevis oocytes, and individual cells were used to measure and correlate the macroscopic rate of GABA transport and the total number
of transporters in the plasma membrane. The two-electrode voltage-clamp method was used to measure the transporter-mediated
macroscopic current evoked by GABA (
), macroscopic charge movements (Q
NaCl) evoked by voltage pulses and whole-cell capacitance. The same cells were then examined by freeze-fracture and electron microscopy
in order to estimate the total number of GAT1 copies in the plasma membrane. GAT1 expression in the plasma membrane led to
the appearance of a distinct population of 9-nm freeze-fracture particles which represented GAT1 dimers. There was a direct
correlation between Q
NaCl and the total number of transporters in the plasma membrane. This relationship yielded an apparent valence of 8 ± 1 elementary
charges per GAT1 particle. Assuming that the monomer is the functional unit, we obtained 4 ± 1 elementary charges per GAT1
monomer. This information and the relationship between and Q
NaCl were used to estimate a GAT1 unitary turnover rate of 15 ± 2 s−1 (21°C, −50 mV). The temperature and voltage dependence of GAT1 were used to estimate the physiological turnover rate to be 79–93 s−1 (37°C, −50 to −90 mV). 相似文献
13.
Raif Musa-Aziz Lihong Jiang Li-Ming Chen Kevin L. Behar Walter F. Boron 《The Journal of membrane biology》2009,228(1):15-31
Others have shown that exposing oocytes to high levels of (10–20 mM) causes a paradoxical fall in intracellular pH (pHi), whereas low levels (e.g., 0.5 mM) cause little pHi change. Here we monitored pHi and extracellular surface pH (pHS) while exposing oocytes to 5 or 0.5 mM NH3/NH4
+. We confirm that 5 mM causes a paradoxical pHi fall (−ΔpHi ≅ 0.2), but also observe an abrupt pHS fall (−ΔpHS ≅ 0.2)—indicative of NH3 influx—followed by a slow decay. Reducing [NH3/NH4
+] to 0.5 mM minimizes pHi changes but maintains pHS changes at a reduced magnitude. Expressing AmtB (bacterial Rh homologue) exaggerates −ΔpHS at both levels. During removal of 0.5 or 5 mM NH3/NH4
+, failure of pHS to markedly overshoot bulk extracellular pH implies little NH3 efflux and, thus, little free cytosolic NH3/NH4
+. A new analysis of the effects of NH3 vs. NH4
+ fluxes on pHS and pHi indicates that (a) NH3 rather than NH4
+ fluxes dominate pHi and pHS changes and (b) oocytes dispose of most incoming NH3. NMR studies of oocytes exposed to 15N-labeled show no significant formation of glutamine but substantial accumulation in what is likely an acid intracellular compartment. In conclusion, parallel measurements of pHi and pHS demonstrate that NH3 flows across the plasma membrane and provide new insights into how a protein molecule in the plasma membrane—AmtB—enhances
the flux of a gas across a biological membrane.
相似文献
Walter F. Boron (Corresponding author)Email: |
14.
Zimmermann D Kiesel M Terpitz U Zhou A Reuss R Kraus J Schenk WA Bamberg E Sukhorukov VL 《The Journal of membrane biology》2008,221(2):107-121
Interactions of structurally dissimilar anionic compounds with the plasma membrane of HEK293 cells were analyzed by patch
clamp and electrorotation. The combined approach provides complementary information on the lipophilicity, preferential affinity
of the anions to the inner/outer membrane leaflet, adsorption depth and transmembrane mobility. The anionic species studied
here included the well-known lipophilic anions dipicrylamine (DPA−), tetraphenylborate (TPB−) and [W2(CO)10(S2CH)]−, the putative lipophilic anion
and three new heterocyclic W(CO)5 derivatives. All tested anions partitioned strongly into the cell membrane, as indicated by the capacitance increase in patch-clamped
cells. The capacitance increment exhibited a bell-shaped dependence on membrane voltage. The midpoint potentials of the maximum
capacitance increment were negative, indicating the exclusion of lipophilic anions from the outer membrane leaflet. The adsorption
depth of the large organic anions DPA−, TPB− and increased and that of W(CO)5 derivatives decreased with increasing concentration of mobile charges. In agreement with the patch-clamp data, electrorotation
of cells treated with DPA− and W(CO)5 derivatives revealed a large dispersion of membrane capacitance in the kilohertz to megahertz range due to the translocation
of mobile charges. In contrast, in the presence of TPB− and no mobile charges could be detected by electrorotation, despite their strong membrane adsorption. Our data suggest that the
presence of oxygen atoms in the outer molecular shell is an important factor for the fast translocation ability of lipophilic
anions. 相似文献
15.
Marilena Martins Pamboukian Soraia Athie Calil Jorge Mariza Gerdulo Santos Adriana Yurie Yokomizo Carlos Augusto Pereira Aldo Tonso 《Cytotechnology》2008,57(1):37-44
Specific respiration rate (
) is a key parameter to understand cell metabolism and physiological state, providing useful information for process supervision
and control. In this work, we cultivated different insect cells in a very controlled environment, being able to measure . Spodoptera frugiperda (Sf9) cells have been used through virus infection as host for foreign protein expression and bioinsecticide production.
Transfected Drosophila melanogaster (S2) cells can be used to produce different proteins. The objective of this work is to investigate respiratory activity and
oxygen transfer during the growth of different insect cells lines as Spodoptera frugiperda (Sf9), Drosophila melanogaster (S2) wild and transfected for the expression of GPV and EGFP. All experiments were performed in a well-controlled 1-L bioreactor,
with SF900II serum free medium. Spodoptera frugiperda (Sf9) cells reached 10.7 × 106 cells/mL and maximum specific respiration rate () of 7.3 × 10−17 molO2/cell s. Drosophila melanogaster (S2) cells achieved 51.2 × 106 cells/mL and of 3.1 × 10–18 molO2/cell s. S2AcGPV (expressing with rabies virus glycoprotein) reached 24.9 × 106 cells/mL and of 1.7 × 10–17 molO2/cell s, while S2MtEGFP (expressing green fluorescent protein) achieved 15.5 × 106 cells/mL and = 1.9 × 10−17 molO2/cell s. Relating to the Sf9, S2 cells reached higher maximum cell concentrations and lower specific respiration rate, which
can be explained by its smaller size. These results presented useful information for scale-up and process control of insect
cells. 相似文献
16.
A carbon membrane-aerated biofilm reactor (CMABR) was developed to treat synthetic wastewater. Such membrane exhibited a high
degree of adhesion and good permeability. Continuous experiments showed that COD and
-N removal efficiency were 90 ± 2 and 92 ± 4% at removal rates of 35.6 ± 3.8 g COD/m2 per day and 9.3 ± 0.6 g
-N/m2 per day, respectively. After 108 days, effluent total nitrogen (TN) kept at 35 ± 4 mg/L when influent
-N increased to 144–164 mg/L and removal efficiency of TN reached 78 ± 3%. Furthermore, Stoichiometric analysis revealed that
70–90% of oxygen supplied was consumed by nitrifier. Scanning electron microscopic (SEM) images and component analysis of
penetrating fluid revealed that extracellular polymeric substance (EPS) adhered to pore and that alkaline washing was an effective
method to remove them. The study demonstrated that carbon membrane could be used as effective gas-permeable membrane in MABR
for wastewater treatment. 相似文献
17.
The effects of 16 different combinations of nutrient load and agitation on yield, nutrient uptake and proximate chemical composition
of the seaweed Ulva lactuca cultured in tanks were evaluated. Intensive fishpond outflow passed through seaweed tanks at four nutrient loading levels
and four water agitation combinations of water exchange, bottom aeration and frequently changing water levels (an accelerated
tide regime). Specific results from these outdoor experiments were examined further under controlled conditions in laboratory
experiments. Agitation treatments affected the performance of U. lactuca only under TAN () load levels below 4 g N m−2 day−1; biofiltration of TAN was the parameter most affected. Biomass yields at each of the four nutrient loading levels were not
significantly different between the agitation treatments. Protein content increased significantly with increasing nutrient
loading. The agitation treatments had a slight effect on seaweed protein content only at the lowest nutrient loading levels.
There were no significant differences in dissolved oxygen concentration, pH, and temperature among the agitation treatments
at all nutrient loading levels. Under laboratory conditions, growth rates, protein content, and photosynthetic and biomass
yield of the seaweed were affected by water velocity under low nutrient concentrations. It is concluded that the effect of
air agitation under the conditions of these experiments was not directly related to photosynthesis, excess dissolved oxygen,
or carbon limitation, but to the diffusion of macro nutrients from the water to the seaweed. Therefore, once nutrient concentrations
are high enough (above about 4 μM of TAN with the other nutrients in their corresponding proportions), aeration per se is
not essential for effective growth and biofiltration by seaweeds. 相似文献
18.
We compared on eight dates during the ice-free period physicochemical properties and rates of phytoplankton and epipelic primary
production in six arctic lakes dominated by soft bottom substrate. Lakes were classified as shallow ( < 2.5 m), intermediate in depth (2.5 m < < 4.5 m), and deep ( > 4.5 m), with each depth category represented by two lakes. Although shallow lakes circulated freely and intermediate and
deep lakes stratified thermally for the entire summer, dissolved oxygen concentrations were always >70% of saturation values.
Soluble reactive phosphorus and dissolved inorganic nitrogen (DIN = NO3
−–N + NH4
+–N) were consistently below the detection limit (0.05 μmol l−1) in five lakes. However, one lake shallow lake (GTH 99) periodically showed elevated values of DIN (17 μmol l−1), total-P (0.29 μmol l−1), and total-N (33 μmol l−1), suggesting wind-generated sediment resuspension. Due to increased nutrient availability or entrainment of microphytobenthos,
GTH 99 showed the highest average volume-based values of phytoplankton chlorophyll a (chl a) and primary production, which for the six lakes ranged from 1.0 to 2.9 μg l−1 and 0.7–3.8 μmol C l−1 day−1. Overall, however, increased resulted in increased area-based values of phytoplankton chl a and primary production, with mean values for the three lake classes ranging from 3.6 to 6.1 mg chl a m−2 and 3.2–5.8 mmol C m−2 day−1. Average values of epipelic chl a ranged from 131 to 549 mg m−2 for the three depth classes, but levels were not significantly different due to high spatial variability. However, average
epipelic primary production was significantly higher in shallow lakes (12.2 mmol C m−2 day−1) than in intermediate and deep lakes (3.4 and 2.4 mmol C m−2 day−1). Total primary production (6.7–15.4 mmol C m−2 day−1) and percent contribution of the epipelon (31–66%) were inversely related to mean depth, such that values for both variables
were significantly higher in shallow lakes than in intermediate or deep lakes.
Handling editor: L. Naselli-Flores 相似文献
19.
The effect of temperature on post-feeding ammonia excretion and oxygen consumption in the southern catfish 总被引:1,自引:0,他引:1
Yiping Luo Xiaojun Xie 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(6):681-689
The post-prandial rates of ammonia excretion (TAN) and oxygen consumption in the southern catfish (Silurus meridionalis) were assessed at 2 h intervals post-feeding until the rates returned to those of the fasting rates, at 17.5, 22.5, 27.5,
and 32.5°C, respectively. Both fasting TAN and increased with temperature, and were lower than those previously reported for many fish species. The relationship between
fasting TAN (mmol NH3–N kg−1 h−1) and temperature (T, °C) was described as: fasting TAN = 0.144e
0.0266T
(r = 0.526, n = 27, P < 0.05). The magnitude of ammonia excretion and its ratio to total N intake during the specific dynamic action (SDA) tended to increase initially, and then decrease with increasing temperature. The
ammonia quotient (AQ), calculated as mol NH3–N/mol O2, following feeding decreased as temperature increased. The relationship between AQ during SDA and temperature was described
as: AQduring SDA = 0.303e
−0.0143T
(r = 0.739, n = 21, P < 0.05). Our results suggest that ammonia excretion and oxygen consumption post-feeding are operating independently of each
other. Furthermore, it appears that the importance of protein as a metabolic substrate in postprandial fish decreases with
temperature. 相似文献
20.
Vallejo-Becerra V Vásquez-Bahena JM Santiago-Hernández JA Hidalgo-Lara ME 《Journal of industrial microbiology & biotechnology》2008,35(11):1289-1295
The recombinant invertase INVB (re-INVB) from Zymomonas mobilis was immobilized on microbeads of Nylon-6, by means of covalent bonding. The enzyme was strongly and successfully bound to
the support. The activity of the free and immobilized enzyme was determined, using 10% (w/v) sucrose, at a temperature ranging
between 15 and 60 °C and a pH ranging between 3.5 and 7. The optimal pH and temperature for the immobilized enzyme were 5.5
and 25 °C, respectively. Immobilization of re-INVB on Nylon-6 showed no significant change in the optimal pH, but a difference
in the optimal temperature was evident, as that for the free enzyme was shown to be 40 °C. The values for kinetic parameters
were determined as: 984 and 98 mM for of immobilized and free re-INVB, respectively. values for immobilized and free enzymes were 6.1 × 102 and 1.2 × 104 s−1, respectively, and immobilized re-INVB showed of 158.73 μmol h min−1 mg−1. Immobilization of re-INVB on Nylon-6 enhanced the thermostability of the enzyme by 50% at 30 °C and 70% at 40 °C, when compared
to the free enzyme. The immobilization system reported here may have future biotechnological applications, owing to the simplicity
of the immobilization technique, the strong binding of re-INVB to the support and the effective thermostability of the enzyme. 相似文献