共查询到20条相似文献,搜索用时 938 毫秒
1.
Reina R 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(8):573-580
Microsphere and morphometric techniques were used to investigate any circulatory changes that accompany secretion by the
salt glands of hatchling Chelonia mydas. Salt glands were activated by a salt load of 27.0 mmol NaCl kg body mass (BM)−1, resulting in a mean sodium secretion rate of 4.14 ± 0.11 mmol Na kg BM−1 h−1 for a single gland. Microsphere entrapment was approximately 160–180 times greater in the active salt gland than the inactive
gland, inferring a similar change in blood flow through salt gland capillaries. The concentration of microspheres trapped
in the salt gland was significantly correlated with the rate of tear production (ml kg BM−1 h−1) and the total rate of sodium secretion (mmol Na kg BM−1 h−1) but not with tear sodium concentration (mmol Na l−1). Adrenaline (500 μg kg BM−1) inhibited tear production within 2 min and reduced microsphere entrapment by approximately 95% compared with active glands.
The volume of filled blood vessels increased from 0.03 ± 0.01% of secretory lobe volume in inactive salt gland sections to
0.70 ± 0.11% in active gland sections. The results demonstrate that capillary blood flow in the salt gland of C. mydas can regulate the activity of the gland as a whole.
Accepted: 12 July 2000 相似文献
2.
Hogstrand C Ferguson EA Galvez F Shaw JR Webb NA Wood CM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(7):461-573
Physiological effects of exposure to silver (AgCln
n−1; 250 μg Ag l−1 or 1000 μg Ag l−1) in seawater fish were investigated using adult starry flounders. While all fish survived up to 10 days in 250 μg Ag l−1, flounders started to die after day 4 in 1000 μg l−1. Dose-dependent increases in plasma and hepatic silver concentrations showed that silver was available for uptake. There
were minimal negative effects on hematological parameters, acid-base status, and blood gases. Plasma ammonia showed a pronounced
(three- to four-fold), but transient increase in flounders exposed to either 250 μg Ag l−1 or 1000 μg Ag l−1. Whole body ammonia and acid equivalent efflux measurements indicated that ammonia retention was due to a combination of
stimulated production and inhibited excretion. In the 1000-μg Ag l−1 group there was a similar transient increase in plasma [magnesium], which was restored by day 4. In contrast, plasma chloride
and sodium levels increased gradually towards the point when fish began to die. At 250 μg Ag l−1, the Na+/K+-ATPase activity of the intestine was unaffected but there was a two-fold increase in branchial Na+/K+-ATPase activity. The latter effect was interpreted as compensation for an elevated chloride and sodium load. The increases
in plasma chloride and sodium concentrations were accompanied by a marked suppression of drinking, thereby indicating that
acute silver toxicity was likely caused by a combination of elevated electrolyte concentrations and dehydration.
Accepted: 9 June 1999 相似文献
3.
G. Gomez R. Voigt J. Atema 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1999,185(5):427-436
To understand how chemoreceptor organs may extract temporal information from odor plumes, we investigated the frequency filter
properties of lobster chemoreceptor cells. We used rapid stimulation and high-resolution stimulus measurement for accurate
stimulus control and recorded extracellular responses from chemoreceptors in the lobster lateral antennule in situ. We tested
16 hydroxyproline-sensitive cells with a series of ten 100-ms pulses at 10, 100 and 1000 μmol l−1 at stimulation frequencies from 0.5 Hz to 4 Hz. Receptor cell responses could accurately encode 10 μmol l−1, but not 100 or 1000 μmol l−1 pulses, delivered at rates of 4 Hz. Flicker-fusion frequency and synchronization with the stimulus pulse train were concentration
dependent: performance rates above 1 Hz became poorer both with increasing pulse amplitude and frequency. Flicker fusion frequency
was 3 Hz for 100 μmol l−1 pulses and 2 Hz for 1000 μmol l−1 pulses. Individual cells showed differences in their stimulus pulse following capabilities, as measured by the synchronization
coefficient. These individual differences may form a basis for coding temporal features of an odor plume in an across-fiber
pattern.
Accepted: 7 July 1999 相似文献
4.
In order to provide a better understanding of the dynamics of phytoplankton in the coastal regions of high latitudes, a study
was carried out to estimate the dynamics of carbon biomass of autotrophic and heterotrophic algal groups over the austral
spring-summer 1997/1998 period. At a fixed station located in the central basin (Paso Ancho) of the Straits of Magellan (53°S),
surface water samples were collected at least once a week from September 1997 (early spring) to March 1998 (late summer).
Quantitative analysis of biomass of phytoplankton was estimated from geometric volumes, using non-linear equations, and converted
to biomass. The pattern of chlorophyll a showed a strong temporal variability, with maximum values (mean 2.8 mg m−3) at the austral spring phytoplankton increase or bloom (October/November) and minimum values during early spring (September:
<0.5 mg m−3) and summer (January/March: 0.5–1.0 mg m−3). During the spring bloom, diatoms made up to 90% of the total phytoplankton carbon (0.01–189 μg l−1), followed by a maximum of thecate dinoflagellates (0.08–34 μg l−1), and sporadic high biomass of phytoflagellates during summer. Heterotrophic algal groups such as Gymnodinium and Gyrodinium spp. dominated (70%, in the 5- to 25-μm size range) shortly before the main diatom bloom, and small peaks were observed within
spring and early summer periods (0–0.4 μg l−1). Phytoflagellates dominated earlier (spring) with higher carbon biomass (8 μg l−1) and post-bloom periods (summer) when carbon biomass ranged between 1 and 4 μg l−1.
Accepted: 6 September 2000 相似文献
5.
Inhibition of Clostridium butyricum by 1,3-propanediol and diols during glycerol fermentation 总被引:3,自引:0,他引:3
1,3-Propanediol inhibition during glycerol fermentation to 1,3-propanediol by Clostridium butyricum CNCM 1211 has been studied. The initial concentration of the 1,3-propanediol affected the growth of the bacterium more than
the glycerol fermentation. μ
max was inversely proportional to the initial concentration of 1,3-propanediol (0–65 g l−1). For glycerol at 20 g l−1, the growth and fermentation were completely stopped at an initial 1,3-propanediol concentration of 65 g l−1. However, for an initial 1,3-propanediol concentration of 50 g l−1 and glycerol at 70 g l−1, the final concentration (initial and produced) of 1,3-propanediol reached 83.7 g l−1(1.1 M), with complete consumption of the glycerol. Therefore, during the fermentation, the strain tolerated a 1,3-propanediol
concentration higher than the initial inhibitory concentration (65 g l−1). The addition of 1,2-propanediol or 2,3-butanediol (50 g l−1) in the presence of glycerol (50–100 g l−1), showed that 2-diols reduced the μ
max in a similar way to 1,3-propanediol. The measurement of the osmotic pressure of glycerol solutions, diols and diol/glycerol
mixtures did not indicate any differences between these compounds. The hypothesis of diol inhibition was discussed. Taking
into account the strain tolerance of highly concentrated 1,3-propanediol during fermentation, the fermentation processes for
optimising production were considered.
Received: 15 November 1999 / Revision received: 1 February 2000 / Accepted: 4 February 2000 相似文献
6.
Andreazza R Okeke BC Pieniz S Brandelli A Lambais MR Camargo FA 《Biological trace element research》2011,143(2):1182-1192
Environmental copper contamination is a serious human health problem. Copper reductase is produced by microorganisms to facilitate
copper uptake by ATPases into the cells increasing copper biosorption. This study assessed the reduction of Cu(II) by cell-free
extracts of a highly copper-resistant bacterium, Pseudomonas sp. strain NA, isolated from vineyard soil contaminated with copper. Both intact cells and cell-free extract of Pseudomonas sp. strain NA displayed substantial reduction of Cu(II). Intact cells reduced more then 80 mg L−1 of Cu(II) from medium amended with 200 mg L−1 of copper after 24 h of incubation. Cell-free extract of the isolate reduced more than 65% of the Cu(II) at initial copper
concentration of 200 mg L−1 after 24 h. Soluble protein production was high at 72 h of incubation at 100 mg L−1 of copper, with more then 60 μg L−1 of total soluble protein in cell-free extract recorded. Cu(II) reduction by isolate NA was increased when copper concentration
increased for both intact cells and cell-free extract. Results indicate that Pseudomonas sp. strain NA produces copper reductase enzyme as the key mechanism of copper biotransformation. 相似文献
7.
A. T. Marshall P. D. Cooper 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,157(6):821-827
Summary The lachrymal salt glands ofChelonia mydas were functional when hatchlings emerged from the nest. Osmotic concentrations up to 720 mosmol kg–1 were recorded in spontaneously produced tears (salt gland secretions). When injected with a Na+ load (1500–2700 mol (100 g)–1) newly emerged hatchlings produced tears ranging in osmotic concentration from 1000–1900 mosmol kg–1 with Na+ secretion rates from single glands of 200–475 mol (100 g·h)–1. In these circumstances the rate of sodium excretion, via the salt glands, was equivalent to the sodium content of 0.2 to 0.5 ml of sea water per hour. Since the apparent drinking rate of hatchlings within the first two days of entering sea water was approximately 0.5 to 1.7 ml per day, the excretion of Na+ imbibed by drinking is well within the secretory capacity of the lachrymal salt glands.In feeding hatchlings extraordinarily high Na+ secretion rates were induced by Na+ loading. Hatchlings which were loaded with Na+ by injection (1500–5400 mol (100 g)–1) produced tears having osmotic concentrations between 1500 and >2000 mosmol kg–1. The Na+ secretion rates from single glands were 750–4185 mol (100 g·h)–1 with extremely high short term rates of 10700 mol (100 g·h)–1 (50 mol min–1 for 28 g hatchlings).In terms of gland mass the highest long term secretion rate translates into 21 mmol of Na+ per gram of salt gland per hour and is the highest secretion rate yet recorded for a reptilian salt gland. This rate is almost three times the highest rate recorded for sea snakes (8 mmol g·h–1) and is similar to rates commonly observed in avian salt glands (25 mmol g·h–1).Secretion by the lachrymal salt glands was initiated by increased blood concentrations of Na+ or K+, K+ being as effective as Na+ but with the composition of the teras being virtually unchanged compared to tears from Na+ stimulated hatchlings. Preliminary experiments indicated that secretion was not initiated by increased Cl– concentration in the blood or by increased volume or osmotic concentration of the blood.Abbreviation
O.P.
osmotic pressure 相似文献
8.
Thomas Rohde Sven Asp Dave A. MacLean Bente K. Pedersen 《European journal of applied physiology and occupational physiology》1998,78(5):448-453
This study examined whether oral glutamine supplementation abolishes some of the exercise-induced changes in lymphocyte functions
following long-term intense exercise. A group of 16 marathon runners participating in The Copenhagen Marathon 1996 were placed
randomly in either a placebo (n = 7) or a glutamine receiving group (n = 9). Each subject received four doses of either placebo or glutamine (100 mg · kg−1) administered at 0, 30, 60, and 90-min post-race. In the placebo group the plasma glutamine concentrations were lower than
pre-race values during the post-exercise period [mean 647 (SEM 32) compared to 470 (SEM 22) μmol · l−1 90-min post-race, P < 0.05] whereas glutamine supplementation maintained the plasma glutamine concentration (at ∼750 μmol · l−1). Glutamine supplementation in vivo had no effect on the lymphokine activated killer (LAK) cell activity, the proliferative
responses or the exercise-induced changes in concentrations or percentages of any of the leucocyte subpopulations examined.
Glutamine addition in in vitro studies enhanced the proliferative response in both groups. These data would suggest that decreased
plasma glutamine concentrations post-exercise are not responsible for exercise-induced decrease in LAK activity and that the
influence of glutamine in vitro is not dependent on the plasma glutamine concentration at the time of sampling.
Accepted: 23 April 1998 相似文献
9.
Kinetic models for astaxanthin production by high cell density mixotrophic culture of the microalga Haematococcus pluvialis 总被引:3,自引:0,他引:3
High cell density cultivation of Haematococcus pluvialis for astaxanthin production was carried out in batch and fed-batch modes in 3.7-L bioreactors with stepwise increased light
intensity control mode. A high cell density of 2.65 g L−1 (batch culture) or 2.74 g L−1 (fed-batch culture) was obtained, and total astaxanthin production in the fed-batch culture (64.36 mg L−1) was about 20.5% higher than in the batch culture (53.43 mg L−1). An unstructured kinetic model to describe the microalga culture system including cell growth, astaxanthin formation, as
well as sodium acetate consumption was proposed. Good agreement was found between the model predictions and experimental data.
The models demonstrated that the optimal light intensity for mixotrophic growth of H. pluvialis in batch or fed-batch cultures in a 3.7-L bioreactor was 90–360 μmol m−2 s−1, and that the stepwise increased light intensity mode could be replaced by a constant light intensity mode.
Received 24 December 1998/ Accepted in revised form 23 April 1999 相似文献
10.
Concentrations of plankton, suspended particles 0.74–87 μm equivalent spherical diameter and dissolved organic carbon (DOC)
were measured from May to February at an Antarctic coastal site. Bacteria-sized particles 0.74–1 μm diameter, and bacterial
cells and heterotrophic protists all exhibited a seasonal minimum during winter and maxima in summer. Bacteria composed <10%
of the bacteria-sized particles. Release of autotrophic protists from the ice caused water column biomass of autotrophs to
reach maximum concentrations in October and November, but maximum cell concentration in the water column was reached in January.
Microheterotroph biomass weakly reflected the release of the ice algal community but reached maximum concentration during
the water column bloom in January. Total DOC concentrations varied from 0.36 mg C l−1 in July to 3.10 mg C l−1 in October, with a yearly average of 1.51 mg C l−1. Ultrafiltration of DOC revealed that the molecular weight composition of the DOC differed greatly through the year. DOC
<5 kDa molecular weight reached a maximum of 1.25 mg C l−1 in October and accounted for up to 60% of total DOC in July. Concentrations of high molecular weight DOC (>100 kDa) were
highest in July and November, with the DOC (100 kDa–0.5 μm) fraction reaching a maximum of 1.22 mg C l−1 in November and composing 82% of the total DOC in January. Wet chemical oxidation and high-temperature catalytic oxidation
organic carbon analyses were compared. Good correlation was observed between methods during summer but no significant correlation
existed in winter, indicating that winter DOC may be refractory.
Accepted: 21 March 2000 相似文献
11.
To test the hypothesis that the contribution of phosphoribulokinase (PRK) to the control of photosynthesis changes depending
on the light environment of the plant, the response of transgenic tobacco (Nicotiana tabacum L.) transformed with antisense PRK constructs to irradiance was determined. In plants grown under low irradiance (330 μmol m−2 s−1) steady-state photosynthesis was limited in plants with decreased PRK activity upon exposure to higher irradiance, with a
control coefficient of PRK for CO2 assimilation of 0.25 at and above 800 μmol m−2 s−1. The flux control coefficient of PRK for steady-state CO2 assimilation was zero, however, at all irradiances in plant material grown at 800 μmol m−2 s−1 and in plants grown in a glasshouse during mid-summer (alternating shade and sun 300–1600 μmol m−2 s−1). To explain these differences between plants grown under low and high irradiances, Calvin cycle enzyme activities and metabolite
content were determined. Activities of PRK and other non-equilibrium Calvin cycle enzymes fructose-1,6-bisphosphatase, sedoheptulose-1,7-bisphosphatase
and ribulose-1,5-bisphosphate carboxylase-oxygenase were twofold higher in plants grown at 800 μmol m−2 s−1 or in the glasshouse than in plants grown at 330 μmol m−2 s−1. Activities of equilibrium enzymes transketolase, aldolase, ribulose-5-phosphate epimerase and isomerase were very similar
under all growth irradiances. The flux control coefficient of 0.25 in plants grown at 330 μmol m−2 s−1 can be explained because low ribulose-5-phosphate content in combination with low PRK activity limits the synthesis of ribulose-1,5-bisphosphate.
This limitation is overcome in high-light-grown plants because of the large relative increase in activities of sedoheptulose-1,7-bisphosphatase
and fructose-1,6-bisphosphatase under these conditions, which facilitates the synthesis of larger amounts of ribulose-5-phosphate.
This potential limitation will have maintained evolutionary selection pressure for high concentrations of PRK within the chloroplast.
Received: 15 November 1999 / Accepted: 27 January 2000 相似文献
12.
Delta-endotoxin production by a strain of Bacillus thuringiensis subsp kurstakion complex media based on crude gruel and fish meal was investigated. High proteolytic activities were concomitantly produced
with the bioinsecticide. In such complex media, the repressive regulation due to readily consumed carbon sources was partially
overcome. In order to improve substrate assimilation, 0.5 g L−1 sodium chloride and 0.1% Tween-80 were supplemented to the production medium, increasing delta-endotoxin yields when using
gruel concentrations below 59 g L−1. At and beyond 75 g L−1 gruel, delta-endotoxin yields were not affected in the presence of 0.5 g L−1 NaCl and 0.1% Tween-80, but proteolytic activity yields were remarkably reduced. Thus, the use of sodium chloride and Tween-80
allowed reduction of the initial gruel concentration to 42 g L−1 for the production of 3350 mg L−1 delta-endotoxin, while it was only 3800 mg L−1 with 92 g L−1 gruel. Moreover, similar to 0.5 g L−1 NaCl and 0.1% Tween-80, the use of 10 g L−1 sodium acetate significantly improved delta-endotoxin production and also reduced the proteolytic activity to 250 U ml−1.
Received 05 November 1998/ Accepted in revised form 19 August 1999 相似文献
13.
Smita Srivastava Ashok Kumar Srivastava 《In vitro cellular & developmental biology. Plant》2012,48(1):73-84
Azadirachtin, a well-known biopesticide, is a secondary metabolite extracted from the seeds of Azadirachta indica. In the present study, azadirachtin was produced in hairy roots of A. indica, generated by Agrobacterium rhizogenes-mediated transformation of leaf explants. Liquid cultures of A. indica hairy roots were developed with a liquid-to-flask volume ratio of 0.15. The kinetics of growth and azadirachtin production
were established in a basal plant growth medium containing MS medium major and minor salts, Gamborg’s medium vitamins, and
30 g l−1 sucrose. The highest azadirachtin accumulation in the hairy roots (up to 3.3 mg g−1) and azadirachtin production (∼44 mg l−1) was obtained on Day 25 of the growth cycle, with a biomass production of 13.3 g l−1 dry weight. To enhance the production of azadirachtin, a Plackett–Burman experimental design protocol was used to identify
key medium nutrients and concentrations to support high root biomass production and azadirachtin accumulation in hairy roots.
The optimal nutrients and concentrations were as follows: 40 g l−1 sucrose, 0.19 g l−1 potassium dihydrogen phosphate, 3.1 g l−1 potassium nitrate, and 0.41 g l−1 magnesium sulfate. Concentrations were determined by a central composite design protocol and verified in shake-flask cultivation.
The optimized medium composition yielded a root biomass production of 14.2 g l−1 and azadirachtin accumulation of 5.2 mg g−1, which was equivalent to an overall azadirachtin production of 73.84 mg l−1, 68% more than that obtained under non-optimized conditions. 相似文献
14.
S. M. E. Guirguis J. C. Yee D. F. Stiffler 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(5):328-334
The skin of intact, free-swimming Xenopus laevis transports Ca2+ inwardly in a manner that is proportional to the external [Ca2+] up to about 0.3 mmol · l−1, saturates above 0.3 mmol · l−1, and is opposed to the electrochemical gradient. Efflux is relatively constant at external concentrations between 0.016 and
0.6 mmol · l−1; net flux which is negative below 0.125 mmol · l−1 becomes positive above this external [Ca2+]. Allometric analysis suggests that both Ca2+ influx and efflux scale to the 2/3 power approximately like surface area. There were no significant differences in influx
between summer and fall animals; however, efflux was greater in the fall and this resulted in a change from positive balance
in the summer to negative balance in the fall. Isolated skins were shown to support a Ca2+ uptake rate of nearly 30 nmol · cm−2 · h−1. The phenylalkylamine verapamil in the apical bathing solution significantly inhibited this at 25 μmol · l−1. The benzothiazepine diltiazem was also effective at 50 μmol · l−1 while the dihydropyradine nifedipine was ineffective up to 100 μmol · l−1. The inorganic ion La3+ was effective at blocking Ca2+ uptake at 300 μmol · l−1; Ni2+ was also effective at 500 μmol · l−1 but Co2+ was ineffective up to 500 μmol · l−1. These results suggest that apical calcium channels in Xenopuslaevis skin have properties similar to mammalian L-channels and fish gill Ca2+ channels.
Accepted: 23 January 1997 相似文献
15.
L. Guglielmo G. C. Carrada G. Catalano A. Dell'Anno M. Fabiano L. Lazzara O. Mangoni A. Pusceddu V. Saggiomo 《Polar Biology》2000,23(2):137-146
Studies on the chemical and biological properties of annual pack ice at a coastal station in Terra Nova Bay (74°41.72′S,
164°11.63′E) were carried out during austral spring at 3-day intervals from 5 November to 1 December 1997. Temporal changes
of nutrient concentrations, algal biomasses, taxonomic composition, photosynthetic pigment spectra and P–E relationships were
studied. Quantity, composition and degradation rates of organic matter in the intact sea ice were also investigated. In addition,
microcosm experiments were carried out to evaluate photosynthetic and photo-acclimation processes of the sympagic flora in
relation to different light regimes. High concentrations of ammonia were measured in four ice-cores (weighted mean values
of the cores ranged from 4.3 ± 1.9 μM to 7.2 ± 3.4 μM), whereas nitrate and phosphate displayed high concentrations (up to
35.9 μM and 7.6 μM, respectively) only in the bottom layer (135–145 cm depth). Particulate carbohydrate and protein concentrations
in the intact sea ice ranged from 0.5 to 2.3 mg l−1 and 0.2 to 2.0 mg l−1, respectively, displaying a notable accumulation of organic matter in the bottom colored layer, where bacterial enzymatic
activities also reached the highest values. Aminopeptidase activity was extremely high (up to 19.7 μM l−1 h−1 ± 0.05 in the bottom layer), suggesting a rapid turnover rate of nitrogen–enriched organic compounds (e.g. proteins). By
contrast, bacterial secondary production was low, suggesting that only a very small fraction of mobilized organic matter was
converted into bacterial biomass (<0.01‰). The sympagic autotrophic biomass (in terms of chlorophaeopigments) of the bottom
layer was high, increasing during the sampling period from 680 to 2480 μg l−1. Analyses of pigments performed by HPLC, as well as microscope observations, indicated that diatoms dominated bottom communities.
The most important species were Amphiprora sp. and Nitschia cfr. stellata. Bottom sympagic communities showed an average P
B
max
of 0.12 mgC mg Chl−1 and low photoadaptation index (E
k=18 μE m−2 s−1, E
m=65 μE m−2 s−1). Results of the microcosm experiment also indicated that communities were photo-oxidized when irradiance exceeded 100 μE m−2 s−1. This result suggests that micro- autotrophs inhabiting sea ice might have a minor role in the pelagic algal blooms.
Accepted: 4 August 1999 相似文献
16.
Laccase, purified from Coriolus versicolor, removed pentachlorophenol (PCP) from solution at pH 5, depending on initial PCP concentration and amount of laccase. With
100 units of laccase, 100% of 25 μg ml−1 PCP and 60% of 200 μg ml−1 PCP were removed respectively over 72 h. No free chloride was released in the reaction. In reaction with 100 μg PCP, products
were primarily polymers (about 80,000 MW) with only 2–3 pg of o- and p-chloranils formed. Polymers were stable to acid hydrolysis and no release of PCP, or other low-molecular-weight products,
was detected over several weeks. Laccase has a potential use in the biotreatment of aqueous effluents containing PCP, with
polymerised products being removed from solution due to their high molecular weight.
Received: 7 June 1999 / Received revision: 18 August 1999 / Accepted: 2 September 1999 相似文献
17.
18.
E. J. Olguín S. Galicia R. Camacho G. Mercado T. J. Pérez 《Applied microbiology and biotechnology》1997,48(2):242-247
The use of untreated sea water supplemented with anaerobic effluents from digested pig waste and sodium bicarbonate was evaluated
as a low-cost medium for semi-continuous cultivation of a mixed culture of two Spirulina strains in outdoor raceways under temperate climatic conditions (pond temperature in the range 21–26 °C and light intensity
in the range 225–957␣μE m−2 s−1). The mixed culture had a predominant population (86.6 ± 3.9%) of an atypical Spirulina strain consisting of straight filaments, which appeared spontaneously after the strain with helicoidal trichomes had been
subcultured. Morphological studies for the identification of the type and size of trichomes of the two strains (HF and SF)
were carried out. The proportions of the two strains were observed to be stable during the monitoring period (30 days). Three
different sets of semicontinuous cultures were carried out. Sets 1 and 2 were operated under regime 1 (a single addition of
anaerobic effluents at time zero and no pH control) during the same season (June and July) of different years. Set 3 was operated
under regime 2 (semi-continuous addition of anaerobic effluents and pH control) during the autumn. A minimum productivity
of 3.6 g m−2 day−1 was obtained at one of the lowest temperatures (22.1 °C) and light intensities (245 μE m−2 s−1) and a maximum productivity of 10.9 g m−2 day−1 was observed at the highest temperature (25 °C) and highest average light intensity (618 μE m−2 s−1) registered for sets 1 and 2. The protein content in the Spirulina biomass harvested from these two sets varied from 17% to 65.6%. In set 3, a maximum productivity of 9.0 g m−2 day−1 was recorded at an average temperature of 24.4 °C and at an average light intensity of 668 μE m−2 s−1. The protein content in this set under regime 2 varied within a narrower range than in set 1 and set 2 (from 34.8% to 49.1%),
apparently because of a continuous availability of ammonia nitrogen at a level of 30–50 mg l−1. However, in terms of the removal of ammonia nitrogen and chemical oxygen demand, regime 1 was more efficient than regime␣2.
Received: 3 September 1996 / Received revision: 19 February 1997 / Accepted: 7 March 1997 相似文献
19.
A fluidized-bed reactor (FBR) was used to enrich an aerobic chlorophenol-degrading microbial culture. Long-term continuous-flow
operation with low effluent concentrations selected oligotrophic microorganisms producing good-quality effluent for pentachlorophenol(PCP)-contaminated
water. PCP biodegradation kinetics was studied using this FBR enrichment culture. The results from FBR batch experiments were
modeled using a modified Haldane equation, which resulted in the following kinetic constants: q
max = 0.41 mg PCP mg protein−1 day−1, K
S = 16 μg l−1, K
i = 5.3 mg l−1, and n = 3.5. These results show that the culture has a high affinity for PCP but is also inhibited by relatively low PCP concentrations
(above 1.1 mg PCP l−1). This enrichment culture was maintained over 1 year of continuous-flow operation with PCP as the sole source of carbon and
energy. During continuous-flow operation, effluent concentrations below 2 μg l−1 were achieved at 268 min hydraulic retention time (t
HR) and 2.5 mg PCP l−1 feed concentration. An increase in loading rate by decreasing t
HR did not significantly deteriorate the effluent quality until a t
HR decrease from 30 min to 21 min resulted in process failure. Recovery from process failure was slow. Decreasing the feed PCP
concentration and increasing t
HR resulted in an improved process recovery.
Received: 10 October 1996 / Received revision: 21 January 1997 / Accepted: 24 January 1997 相似文献
20.
The influence of ammonia on the anaerobic degradation of peptone by mesophilic and thermophilic populations of biowaste was
investigated. For peptone concentrations from 5 g l−1 to 20 g l−1 the mesophilic population revealed a higher rate of deamination than the thermophilic population, e.g. 552 mg l−1 day−1 compared to 320 mg l−1 day−1 at 10 g l−1 peptone. The final degree of deamination of the thermophilic population was, however, higher: 102 compared to 87 mg NH3/g peptone in the mesophilic cultures. If 0.5–6.5 g l−1 ammonia was added to the mesophilic biowaste cultures, deamination of peptone, degradation of its chemical oxygen demand
(COD) and formation of biogas were increasingly inhibited, but no hydrogen was formed. The thermophilic biowaste cultures
were most active if around 1 g ammonia l−1 was present. Deamination, COD degradation and biogas production decreased at lower and higher ammonia concentrations and
hydrogen was formed in addition to methane. Studies of the inhibition by ammonia of peptone deamination, COD degradation and
methane formation revealed a K
i (50%) for NH3 of 92, 95 and 88 mg l−1 at 37 °C and 251, 274 and 297 mg l−1 at 55 °C respectively. This indicated that the thermophilic flora tolerated significantly more NH3 than the mesophilic flora. In the mesophilic reactor effluent 4.6 × 108 peptone-degrading colony-forming units (cfu)/ml were culturable, whereas in the thermophilic reactor effluent growth of only
5.6 × 107 cfu/ml was observed.
Received: 24 April 1998 / Received revision: 26 June 1998 / Accepted: 27 June 1998 相似文献