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1.
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
2.
Codium fragile (Suringar) Hariot is an edible green alga farmed in Korea using seed stock produced from regeneration of isolated utricles
and medullary filaments. Experiments were conducted to reveal the optimal conditions for nursery culture and out-growing of
C. fragile. Sampling and measurement of underwater irradiance were carried out at farms cultivating C. fragile at Wando, on the southwestern coast of Korea, from October 2004 to August 2005. Growth of erect thalli and underwater irradiance
were measured over a range of depths for three culture stages. During the nursery cultivation stage (Stage I), growth rate
was greatest at 0.5 m depth (0.055 ± 0.032 mm day−1), where the average midday irradiance over 60 days was 924 ± 32 μmol photons m−2 s−1. During the pre-main cultivation stage (Stage II), the greatest growth rate occurred at a depth of 2 m (0.113 ± 0.003 mm day−1) with an average irradiance of 248 ± 116 μmol photons m−2 s−1. For the main cultivation stage (Stage III) of the alga, thalli achieved the greatest increase in biomass at 1 m depth (7.2 ± 1.0 kg
fresh wt m−1). These results suggest that optimal growth at each cultivation stages of C. fragile could be controlled by depth of cultivation rope. 相似文献
3.
A. Robic D. Bertrand J.-F. Sassi Y. Lerat M. Lahaye 《Journal of applied phycology》2009,21(4):451-456
The water-soluble cell wall polysaccharides from green seaweeds of Ulva spp. (Ulvales, Chlorophyta), referred to as ulvan, demonstrate composition- and structure-related functional properties.
Mid-infrared spectroscopy combined with chemometric techniques was investigated as a means to rapidly predict the chemical
composition of ulvan extracts. A calibration was realized with 41 ulvan extracts from two Ulva species. The variables studied included the constituent sugars (rhamnose, xylose, glucose, galactose, glucuronic acid, iduronic
acid), protein, and sulfate contents. The correlation between Fourier transform infrared and chemical data was developed using
partial least squares (PLS) regression with full cross-validation (leave one out). The coefficients of determination in cross-validation
() and the standard error in cross-validation were determined for each variable. The PLS model validation resulted in a coefficient
of determination () and a standard error in prediction. Good predictions were obtained for rhamnose ( = 0.9244), xylose ( = 0.8758), glucuronic acid ( = 0.9415), and sulfate ( = 0.9218), which are the main ulvan constituents. However, minor components such as proteins, glucose, galactose, and iduronic
acid were not correctly predicted. This study showed that mid-infrared spectroscopy combined with PLS regression is a reliable
and fast method for the quantification of the main chemical constituents of ulvan extracts. 相似文献
4.
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
5.
White rot fungi are a promising option to treat recalcitrant organic molecules, such as lignin, polycyclic aromatic hydrocarbons,
and textile dyes, because of the lignin-modifying enzymes (LMEs) they secrete. Because knowledge of the kinetic parameters
is important to better design and operate bioreactors to cultivate these fungi for degradation and/or to produce LME(s), these
parameters were determined using Trametes versicolor ATCC 20869 (ATCC, American Type Culture Collection) in a magnetic stir bar reactor. A complete set of kinetic data has not
been previously published for this culture. Higher than previously reported growth rates with high laccase production of up
to 1,385 U l−1 occurred during growth without or glucose limitation. The maximum specific growth rate averaged 0.94 ± 0.23 day−1, whereas the maximum specific substrate consumption rates for glucose and ammonium were 3.37 ± 1.16 and 0.15 ± 0.04 day−1, respectively. The maximum specific oxygen consumption rate was 1.63 ± 0.36 day−1. 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.
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
10.
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
11.
Soil temperature and biotic factors drive the seasonal variation of soil respiration in a maize (Zea mays L.) agricultural ecosystem 总被引:1,自引:0,他引:1
Guangxuan Han Guangsheng Zhou Zhenzhu Xu Yang Yang Jingli Liu Kuiqiao Shi 《Plant and Soil》2007,291(1-2):15-26
The diurnal and seasonal variation of soil respiration (SR) and their driving environmental factors were studied in a maize
ecosystem during the growing season 2005. The diurnal variation of SR showed asymmetric patterns, with the minimum occurring
around early morning and the maximum around 13:00 h. SR fluctuated greatly during the growing season. The mean SR rate was
3.16 μmol CO2 m−2 s−1, with a maximum of 4.87 μmol CO2 m−2 s−1 on July 28 and a minimum of 1.32 μmol CO2 m−2 s−1 on May 4. During the diurnal variation of SR, there was a significant exponential relationship between SR and soil temperature
(T) at 10 cm depth:
. At a seasonal scale, the coefficient α and β fluctuated because the biomass (B) increased α, and the net primary productivity (NPP) of maize markedly increased β of the exponential equation. Based on this, we developed the equation
to estimate the magnitude of SR and to simulate its temporal variation during the growth season of maize. Most of the temporal
variability (93%) in SR could be explained by the variations in soil temperature, biomass and NPP of maize. This model clearly
demonstrated that soil temperature, biomass and NPP of maize combined to drive the seasonal variation of SR during the growing
season. However, only taking into account the influence of soil temperature on SR, an exponential equation over- or underestimated
the magnitude of SR and resulted in an erroneous representation of the seasonal variation in SR. Our results highlighted the
importance of biotic factors for the estimation of SR during the growing season. It is suggested that the models of SR on
agricultural sites should not only take into account the influence of soil temperature, but also incorporate biotic factors
as they affect SR during the growing season. 相似文献
12.
A method based on the fluorescence probe 8-hydroxypyrene-1,3,6-trisulfonic acid for in situ measurement of pH in partly frozen
aqueous solutions was developed using multifrequency, phase-modulated fluorescence spectroscopy inherently correcting for
light scattering. The probe was determined to have pK
a = 7.72 ± 0.03 at 25.0 °C extrapolated to zero ionic strength with as derived from temperature dependence (5 to 25 °C investigated). Ionic strength dependence of pK
a determined experimentally was described using Debye–Hückel formalism for ionic strength up to 3 M. Temperature and ionic
strength dependence were combined to yield for determination of pH at subzero temperatures with α experimentally determined from the ratio between fluorescence intensity after excitation at 454 and 415 nm, α = FI(454 nm)/2.5·FI(415 nm). Fluorescence could be described as a decay of a single excited state with a fluorescence life
time of 5.40 ± 0.05 ns at 25 °C, and excited state acid–base equilibration was shown not to interfere with the pH measurement.
Using the method, pH of a 0.25 M phosphate buffer with pH = 6.8 at 25 °C was shown to decrease gradually to pH = 4.2 in the
ice slurry at −13 °C. 相似文献
13.
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
14.
Han Gil Choi Ki Hoon Lee Hyun Il Yoo Pil Jun Kang Young Sik Kim Ki Wan Nam 《Journal of applied phycology》2008,20(5):729-735
The effects of temperature, irradiance, and daylength on Sargassum horneri growth were examined at the germling and adult stages to discern their physiological differences. Temperature–irradiance
(10, 15, 20, 25, 30°C × 20, 40, 80 μmol photons m−2s−1) and daylength (8, 12, 16, 24 h) experiments were carried out. The germlings and blades of S. horneri grew over a wide range of temperatures (10–25°C), irradiances (20–80 μmol photons m−2s−1), and daylengths (8–24 h). At the optimal growth conditions, the relative growth rates (RGR) of the germlings were 21% day−1 (25°C, 20 μmol photons m−2s−1) and 13% day−1 (8 h daylength). In contrast, the RGRs of the blade weights were 4% day−1 (15°C, 20 μmol photons m−2s−1) and 5% day−1 (12 h daylength). Negative growth rates were found at 20 μmol photons m−2s−1 of 20°C and 25°C treatments after 12 days. This phenomenon coincides with the necrosis of S. horneri blades in field populations. In conclusion, we found physiological differences between S. horneri germlings and adults with respect to daylength and temperature optima. The growth of S. horneri germlings could be enhanced at 25°C, 20 μmol photons m−2s−1, and 8 h daylength for construction of Sargassum beds and restoration of barren areas. 相似文献
15.
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
16.
The data processing method of the turbidimetric bioassay of nisin was modified to facilitate its industrial application. The
influence of the initial indicator concentration was minimized by a redefined specific dose of the bacteriocin as the quotient
between the titer of the added bacteriocin and the initial population density of the indicator in the suspension. It was found
that d
c = 0.125 μg ml−1 was the critical dose of nisin that can cause a complete inhibition of the indicator, Pediococcus acidilactici UL5, with an initial OD of 0.135. To eliminate the interference of the cell debris, an equation, , exploiting d
c, was formulated to obtain the intrinsic survival proportion. The use of the specific dose of the bacteriocin and the intrinsic
survival proportion as parameters of the dose/response curve greatly enhanced its repeatability and feasibility. A dual-dosage
approach was developed to further simplify the conventional standard dose/response curve method. 相似文献
17.
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
18.
Lamia Trabelsi Hatem Ben Ouada Hassen Bacha Mohamed Ghoul 《Journal of applied phycology》2009,21(4):405-412
The effects of light intensity and temperature on Arthrospira platensis growth and production of extracellular polymeric substances (EPS) in batch culture were evaluated using a three-level, full-factorial
design and response surface methodology. Three levels were tested for each parameter (temperature: 30, 35, 40°C; light intensity:
50, 115, 180 μmol photons m−2 s−1). Both growth and EPS production are influenced mainly by the temperature factor but the interaction term temperature*light
intensity also had a significant effect. In addition, conditions optimising EPS production are different from those optimising
growth. The highest growth rate (0.414 ± 0.003 day−1) was found at the lowest temperature (30°C) and highest light intensity (180 μmol photons m−2 s−1) tested, no optima were detectable within the given test range. Obviously, optima for growth must be at a temperature lower
than 30°C and a light intensity higher than 180 μmol photons m−2 s−1. For EPS production, light intensity had a positive linear effect (optimum obviously higher than 180 μmol photons m−2 s−1), but for the temperature parameter a maximum effect was detectable at 35°C. 相似文献
19.
Ganka Chaneva Sevdalina Furnadzhieva Kaledona Minkova Jaromir Lukavsky 《Journal of applied phycology》2007,19(5):537-544
The effect of light intensity (50–300 μmol photons m−2 s−1) and temperature (15–50°C) on chlorophyll a, carotenoid and phycobiliprotein content in Arthronema africanum biomass was studied. Maximum growth rate was measured at 300 μmol photons m−2 s−1 and 36°C after 96 h of cultivation. The chlorophyll a content increased along with the increase in light intensity and temperature and reached 2.4% of dry weight at 150 μmol photons
m−2 s−1 and 36°C, but it decreased at higher temperatures. The level of carotenoids did not change significantly under temperature
changes at illumination of 50 and 100 μmol photons m−2 s−1. Carotenoids were about 1% of the dry weight at higher light intensities: 150 and 300 μmol photons m−2 s−1. Arthronema africanum contained C-phycocyanin and allophycocyanin but no phycoerythrin. The total phycobiliprotein content was extremely high,
more than 30% of the dry algal biomass, thus the cyanobacterium could be deemed an alternative producer of C-phycocyanin.
A highest total of phycobiliproteins was reached at light intensity of 150 μmol photons m−2 s−1 and temperature of 36°C, C-phycocyanin and allophycocyanin amounting, respectively, to 23% and 12% of the dry algal biomass.
Extremely low (<15°C) and high temperatures (>47°C) decreased phycobiliprotein content regardless of light intensity. 相似文献
20.
Summary. Presented here is the first experimental evidence that natural, intramolecular, isotope ratios are sensitive to physiological
status, based on observations of intramolecular δ15N of lysine in the mitochondrial mimic Paracoccus denitrificans. Paracoccus denitrificans, a versatile, gram-negative bacterium, was grown either aerobically or anaerobically on isotopically-characterized ammonium
as sole cell-nitrogen source. Nitrogen isotope composition of the biomass with respect to source ammonium was
= −6.2 ± 1.2‰ for whole cells under aerobic respiration, whereas cells grown anaerobically produced no net fractionation
(
= −0.3 ± 0.23‰). Fractionation of 15N between protein nitrogen and total cell nitrogen increased during anaerobic respiration and suggests that residual nitrogen-containing
compounds in bacterial cell membranes are isotopically lighter under anaerobic respiration. In aerobic cells, the lysine intramolecular
difference between peptide and sidechain nitrogen is negligible, but in anaerobic cells was a remarkable Δ15Np − s = δ15Npeptide − δ15Nsidechain = +11.0‰, driven predominantly by enrichment at the peptide N. Consideration of known lysine pathways suggests this to be
likely due to enhanced synthesis of peptidoglycans in the anaerobic state. These data indicate that distinct pathway branching
ratios associated with microbial respiration can be detected by natural intramolecular Δδ15N measurements, and are the first in vivo observations of position-specific measurements of nitrogen isotope fractionation. 相似文献