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1.
Cell density and fatty acid (FA) content of Pavlova lutheri and Chaetoceros muelleri were analysed in a continuous algal production system (250-L bags) with reduced diameter. The cell density and FA content
and composition in the algal production system were determined in replicate bags over a period of 5 weeks. The results showed
that the cell density and essential FAs increased during the experiment for both species. After 5 weeks the mean cell numbers
had increased to 6.0 ± 0.3 × 106 cells mL−1 in the P. lutheri bags and 6.0 ± 0.4 × 106 cells mL−1 in the C. muelleri bags. The content of total FAs increased significantly (p < 0.05) in all of the bags during the experiment. At the end of the experiment the mean total FA content were 2.7 ± 0.3 pg cell−1 in the P. lutheri bags and 1.8 ± 0.1 pg cell−1 in the C. muelleri bags. Maximum total FA content registered was 3.0 pg cell−1 in one of the P. lutheri bags. The content of the essential FAs (ARA, EPA, DHA) increased over time in both of the species. At the end of the experiment
the content of EPA (0.6 ± 0.1 pg cell−1) and DHA (0.3 ± 0.0 pg cell−1) were highest in the P. lutheri bags, while ARA (0.1 ± 0.0 pg cell−1) was highest in C. muelleri. EPA and DHA constituted 22% and 11%, respectively, of total FA content in P. lutheri, while ARA constituted 6% of total FA content in C. muelleri. The results from this experiment indicate that flagellates such as P. lutheri perform better in narrow bags with improved light conditions, while diatoms like C. muelleri perform better in wider bags under light limitation. Implications for bivalve hatcheries are discussed. 相似文献
2.
The methylotrophic yeast Pichia pastoris has been used for the expression of many proteins. However, limitations such as protein degradation and aggregation became
obvious when secreting heterologous protein-recombinant human consensus interferon-α mutant. Here, we investigate the effect
of induction temperature on the yield and stability of interferon mutant expressed by P. patoris with buffered complex medium. The best results in terms of interferon mutant bioactivity and specific bioactivity were obtained
when the microorganism was induced at 15°C, which were 2.91 × 108 ± 0.3 × 108 and 2.26 × 108 ± 0.23 × 108 IU mg−1, respectively. At the same time, the cells grew fast owing to high AOX1-specific activity, and interferon mutant expression
level reached 1.23 g l−1, which was almost 30 times higher than that in the flask. Also, the proteolytic degradation of interferon mutant was inhibited
completely because of lower protease bioactivity probably due to a reduced cell death rate at lower temperatures as well as
protection of yeast extract and peptone in complex medium. In addition, interferon mutant aggregation was repressed significantly
by the addition of Tween-80, and a specific bioactivity of 7.35 × 108 ± 0.56 × 108 IU mg−1 was obtained. These results should be applicable to other low-stability recombinant proteins expressed in P. pastoris. 相似文献
3.
Ten accessions belonging to the Brassica oleracea subspecies alba and rubra, and to B. oleracea var. sabauda were used in this study. Protoplasts were isolated from leaves and hypocotyls of in vitro grown plants. The influence of selected factors on the yield, viability, and mitotic activity of protoplasts immobilized
in calcium alginate layers was investigated. The efficiency of protoplast isolation from hypocotyls was lower (0.7 ± 0.1 × 106 ml−1) than for protoplasts isolated from leaf mesophyll tissue (2 ± 0.1 × 106 ml−1). High (70–90%) viabilities of immobilized protoplasts were recorded, independent of the explant sources. The highest proportion
of protoplasts undergoing divisions was noted for cv. Reball F1, both from mesophyll (29.8 ± 2.2%) and hypocotyl (17.5 ± 0.3%)
tissues. Developed colonies of callus tissue were subjected to regeneration and as a result plants from six accessions were
obtained. 相似文献
4.
Maple sap, an abundant natural product especially in Canada, is rich in sucrose and thus may represent an ideal renewable
feedstock for the production of a wide variety of value-added products. In the present study, maple sap or sucrose was employed
as a carbon source to Alcaligenes latus for the production of poly-β-hydroxybutyrate (PHB). In shake flasks, the biomass obtained from both the sap and sucrose were
4.4 ± 0.5 and 2.9 ± 0.3 g/L, and the PHB contents were 77.6 ± 1.5 and 74.1 ± 2.0%, respectively. Subsequent batch fermentation
(10 L sap) resulted in the formation of 4.2 ± 0.3 g/L biomass and a PHB content of 77.0 ± 2.6%. The number average molecular
weights of the PHB produced by A. latus from maple sap and pure sucrose media were 300 ± 66 × 103 and 313 ± 104 × 103 g/mol, respectively. Near-infrared, 1H magnetic resonance imaging (MRI), and 13C-MRI spectra of the microbially produced PHB completely matched those obtained with a reference material of poly[(R)-3-hydroxybutyric
acid]. The polymer was found to be optically active with [α]25
D equaled to −7.87 in chloroform. The melting point (177.0°C) and enthalpy of fusion (77.2 J/g) of the polymer were also in
line with those reported, i.e., 177°C and 81 J/g, respectively. 相似文献
5.
Little bluestem plants (Schizachyrium scoparium (Michx.) Nash) were grown in fumigated and nonfumigated soil under manipulated levels of three inorganic nutrients: nitrogen, phosphorus, or bases (Ca + Mg). Plants grown in nonfumigated soil had significantly (P < 0.05) higher tissue levels of inorganic nutrients (Cu, Zn, Al, S, Mg, Mn, Ca, and P), smaller shoots, less total biomass, fewer flowering plants but more VAM fungal colonization than plants grown in fumigated soil that were essentially nonmycorrhizal (colonization vs. 1.2 ± 4.9%, for plants grown in nonfumigated and fumigated soil, respectively). Levels of phosphorus (14–33 μg/g) available (Bray No. 1) in the soil prior to manipulation, which are adequate for little bluestem, likely resulted in the development of an ineffectual mycorrhizal association, which in turn, caused the depressed growth of plants in nonfumigated soil. Among plants grown in nonfumigated soil, there was significant variation in VAM fungal colonization and sporulation owing to nutrient treatment. Nitrogen treatment and deionized water control had significantly lower levels of colonization than phosphorus and base treatments. However, plants in the nitrogen and base treatments had significantly more spores/100 cc of rhizosphere soil than plants grown in the deionized water control. 相似文献
6.
Kallistova AY Kevbrina MV Nekrasova VK Shnyrev NA Einola JK Kulomaa MS Rintala JA Nozhevnikova AN 《Microbial ecology》2007,54(4):637-645
The enumeration of methanotrophic bacteria in the cover soil of an aged municipal landfill was carried out using (1) fluorescent
in situ hybridization (FISH) with horseradish peroxidase-labeled oligonucleotide probes and tyramide signal amplification, also known
as catalyzed reporter deposition-FISH (CARD-FISH), and (2) most probable number (MPN) method. The number of methanotrophs
was determined in cover soil samples collected during April–November 2003 from a point with low CH4 emission. The number of types I and II methanotrophs obtained by CARD-FISH varied from 15 ± 2 to 56 ± 7 × 108 cells g−1 absolute dry mass (adm) of soil and methanotrophs of type I dominated over type II. The average number of methanotrophs throughout
the cover soil profile was highest during May–September when the cover soil temperature was above 13°C. Methanotrophs accounted
for about 50% of the total bacterial population in the deepest cover soil layer owing to higher availability of substrate
(CH4). A lower number of methanotrophs (7 × 102 to 17 × 105 cells g−1 adm of soil) was determined by the MPN method compared to the CARD-FISH counts, thus confirming previous results that the
MPN method is limited to the estimation of the culturable species that can be grown under the incubation conditions used.
The number of culturable methanotrophs correlated with the methane-oxidizing activity measured in laboratory assays. In comparison
to the incubation-based measurements, the number of methanotrophs determined by CARD-FISH better reflected the actual characteristics
of the environment, such as release and uptake of CH4, temperature, and moisture, and availability of substrates. 相似文献
7.
Emanuelli M Cecati M Sartini D Stortoni P Corradetti A Giannubilo SR Turi A Tranquilli AL 《Cell stress & chaperones》2009,14(2):193-197
AHSP inhibits cellular production of the reactive oxygen species. Reduced AHSP indicates reduced protection against oxidative
stressors. Our objective was to investigate AHSP levels in recurrent miscarriage (RM). Trophoblast was collected from women
of 10 weeks gestation: voluntary abortion controls (VA, n = 10); spontaneous first miscarriage with subsequent normal pregnancy (SMSN, n = 15) or with subsequent miscarriage (SMSM, n = 5); RM previously investigated (RMPS, n = 5) or not previously investigated (RM, n = 5). AHSP mRNA and protein were determined using real-time quantitative polymerase chain reaction (PCR) and Western blot,
respectively. One-way ANOVA was performed to assess statistical significance (p < 0.05). ahsp mRNA levels were maximally reduced in RM and RMPS (8.0 × 10−6 ± 1.3 and 8.1 × 10−6 ± 0.7, respectively) compared with SMSN and VA (16.1 × 10−6 ± 2.3 and 26.1 × 10−6 ± 2.7, respectively). SMSM showed levels significantly reduced as well (9.0 × 10−6 ± 2.3). In RM, a reduced defense from oxidative stressors is evident at first miscarriage, identifying women at high risk
for subsequent eventful pregnancy. Reduced AHSP may identify women at risk of experiencing further miscarriages.
Monica Emanuelli and Monia Cecati contributed equally to this paper. 相似文献
8.
Ribitsch D Karl W Wehrschütz-Sigl E Tutz S Remler P Weber HJ Gruber K Stehr R Bessler C Hoven N Sauter K Maurer KH Schwab H 《Applied microbiology and biotechnology》2009,81(5):875-886
In the course of a microbial screening of soil samples for new oxidases, different enrichment strategies were carried out.
With choline as the only carbon source, a microorganism was isolated and identified as Arthrobacter nicotianae. From this strain, a gene coding for a choline oxidase was isolated from chromosomal DNA. This gene named codA was cloned in Escherichia coli BL21-Gold and the protein (An_CodA) heterologously overexpressed as a soluble intracellular protein of 59.1 kDa. Basic biochemical characterization of
purified protein revealed a pH optimum of 7.4 and activity over a broad temperature range (15–70 °C). Specific activities
were determined toward choline chloride (4.70 ± 0.12 U/mg) and the synthetic analogs bis(2-hydroxyethyl)-dimethylammonium
chloride (0.05 ± 0.45 × 10–2 U/mg) and tris-(2-hydroxyethyl)-methylammonium methylsulfate (0.01 ± 0.12 × 10–2 U/mg). With increasing number of oxidizable groups, a significant decrease in activity was noted. Determination of kinetic
parameters in atmorspheric oxygen resulted in K
M = 1.51 ± 0.09 mM and V
max = 42.73 ± 0.42 mU/min for choline chloride and K
M = 4.77 ± 0.76 mM and V
max = 48.40 ± 2.88 mU/min for the reaction intermediate betaine aldehyde respectively. Nuclear magnetic resonance spectroscopic
analysis of the products formed during the enzyme reaction with choline chloride showed that in vitro the intermediate betaine
aldehyde exists also free in solution. 相似文献
9.
Tree species and wood ash application in plantations of short-rotation woody crops (SRWC) may have important effects on the
soil productive capacity through their influence on soil organic matter (SOM) and exchangeable cations. An experiment was
conducted to assess changes in soil C and N contents and pH within the 0–50 cm depth, and exchangeable cation (Ca2+, Mg2+, K+, and Na+) and extractable acidity concentrations within the 0–10 cm depth. The effects of different species (European larch [Larix decidua P. Mill.], aspen [Populus tremula L. × Populus tremuloides Michx.], and four poplar [Populus spp.] clones) and wood ash applications (0, 9, and 18 Mg ha−1) on soil properties were evaluated, using a common garden experiment (N = 70 stands) over 7 years of management in Michigan’s Upper Peninsula. Soils were of the Onaway series (fine-loamy, mixed,
active, frigid Inceptic Hapludalfs). The NM-6 poplar clone had the greatest soil C and N contents in almost all ash treatment
levels. Soil C contents were 7.5, 19.4, and 10.7 Mg C ha−1 greater under the NM-6 poplar than under larch in the ash-free, medium-, and high-level plots, respectively. Within the surface
layer, ash application increased soil C and N contents (P < 0.05) through the addition of about 0.7 Mg C ha−1 and 3 kg N ha−1 with the 9 Mg ha−1 ash application (twofold greater C and N amounts were added with the 18 Mg ha−1 application). During a decadal time scale, tree species had no effects—except for K+—on the concentrations of the exchangeable cations, pH, and extractable acidity. In contrast, ash application increased soil
pH and the concentration of Ca2+ (P < 0.05), from 5.2 ± 0.4 cmolc kg−1 (ash-free plots) to 8.6 ± 0.4 cmolc kg−1 (high-level ash plots), and tended to increase the concentration of Mg2+ (P < 0.1), while extractable acidity was reduced (P < 0.05) from 5.6 ± 0.2 cmolc kg−1 (ash-free plots) to 3.7 ± 0.2 cmolc kg−1 (high-level plots). Wood ash application, within certain limits, not only had a beneficial effect on soil properties important
to the long-term productivity of fast-growing plantations but also enhanced long-term soil C sequestration. 相似文献
10.
Brass coupons (70% Cu 30% Zn) were exposed to a cooling freshwater system of an oil refinery, in order to investigate susceptibility
of the metal to biofilm formation. The coupons were fixed on bypasses at points which allowed the circulation of makeup, cooling
and return water. The number of aerobic, anaerobic and sulfate-reducing bacteria was determined in both the planktonic and
the sessile phases. Maximum bacterial concentrations were detected in the cooling water, corresponding to 2.1 ± 0.1 × 106 CFU ml−1 (planktonic phase) and 1.3 ± 0.2 × 105 CFU cm−2 (sessile phase) for aerobic bacteria and to 3.2 ± 0.3 × 105 cells ml−1 (planktonic phase) and 6.2 ± 0.7 × 105 cells cm−2 (sessile phase) for anaerobic bacteria. Sulfate-reducing bacteria (SRB) were observed only in the planktonic phase, being
found in greater numbers in the return water. Scanning electron microscopy (SEM) analysis indicated that biofilm formation
occurred at the three monitored sites and showed a diversity in cell morphology. Nonetheless, no evidence of corrosion was
observed on the brass coupons during the experimental period.
Received 22 May 1997/ Accepted in revised form 19 September 1997 相似文献
11.
In this study, sludge was taken from a municipal wastewater treatment plant that contained a nearly equal number of archaeal
amoA genes (5.70 × 106 ± 3.30 × 105 copies mg sludge−1) to bacterial amoA genes (8.60 × 106 ± 7.64 × 105 copies mg sludge−1) and enriched in three continuous-flow reactors receiving an inorganic medium containing different ammonium concentrations:
2, 10, and 30 mM NH4+–N (28, 140, and 420 mg N l−1). The abundance and communities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in enriched nitrifying
activated sludge (NAS) were monitored at days 60 and 360 of the operation. Early on, between day 0 and day 60 of reactor operation,
comparative abundance of AOA amoA genes to AOB amoA genes varied among the reactors depending on the ammonium levels found in the reactors. As compared to the seed sludge, the
number of AOA amoA genes was unchanged in the reactor with lower ammonium level (0.06 ± 0.04 mgN l−1), while in the reactors with higher ammonium levels (0.51 ± 0.33 and 0.25 ± 0.10 mgN l−1), the numbers of AOA amoA genes were deteriorated. By day 360, AOA disappeared from the ammonia-oxidizing consortiums in all reactors. The majority
of the AOA sequences from all NASs at each sampling period fell into a single AOA cluster, however, suggesting that the ammonium
did not affect the AOA communities under this operational condition. This result is contradictory to the case of AOB, where
the communities varied significantly among the NASs. AOB with a high affinity for ammonia were present in the reactors with
lower ammonium levels, whereas AOB with a low affinity to ammonia existed in the reactors with higher ammonium levels. 相似文献
12.
The community structure and diversity of anaerobic ammonium oxidation (anammox) bacteria in the surface sediments of equatorial
Pacific were investigated by phylogenic analysis of 16S rRNA and hydrazine oxidoreductase (hzo) genes and PCoA (principal coordinates analysis) statistical analysis. Results indicated that 16S rRNA and hzo sequences in the P2 (off the center of western Pacific warm pool) and P3 (in the eastern equatorial Pacific) sites all belong
to the Candidatus “Scalindua”, the dominate anammox bacteria in the low-temperature marine environment proved by previous studies. However,
in the P1 site (in center of warm pool of western Pacific), large part of 16S rRNA gene sequences formed a separated cluster.
Meanwhile, hzo gene sequences from P1 sediment also grouped into a single cluster. PCoA analysis demonstrated that the anammox community
structure in the P1 has significant geographical distributional difference from that of P2, P3, and other marine environments
based on 16S rRNA and hzo genes. The abundances of anammox bacteria in surface sediments of equatorial Pacific were quantified by q-PCR analysis of hzo genes, which ranged from 3.98 × 103 to 1.17 × 104 copies g−1 dry sediments. These results suggested that a special anammox bacteria phylotypes exist in the surface sediment of the western
Pacific warm pool, which adapted to the specific habitat and maybe involved in the nitrogen loss process from the fixed inventory
in the habitat. 相似文献
13.
Water conductance of the cuticular membrane (CM) of mature sweet cherry fruit (Prunus avium L. cv. Sam) was investigated by monitoring water loss from segments of the outer pericarp excised from the cheek of the fruit.
Segments consisted of epidermis, hypodermis and several cell layers of the mesocarp. Segments were mounted in stainless-steel
diffusion cells with the mesocarp surface in contact with water, while the outer cuticular surface was exposed to dry silica
(22 ± 1 °C). Conductance was calculated by dividing the amount of water transpired per unit area and time by the difference
in water vapour concentration across the segment. Conductance values had a log normal distribution with a median of 1.15 × 10−4 m s−1 (n=357). Transpiration increased linearly with time. Conductance remained constant and was not affected by metabolic inhibitors
(1 mM NaN3 or 0.1 mM carbonylcyanide m-chlorophenylhydrazone) or thickness of segments (range 0.8–2.8 mm). Storing fruit (up to 42 d, 1 °C) used as a source of
segments had no consistent effect on conductance. Conductance of the CM increased from cheek (1.16 ± 0.10 × 10−4 m s−1) to ventral suture (1.32 ± 0.07 × 10−4 m s−1) and to stylar end (2.53 ± 0.17 × 10−4 m s−1). There was a positive relationship (r2=0.066**; n=108) between conductance and stomatal density. From this relationship the cuticular conductance of a hypothetical astomatous
CM was estimated to be 0.97 ± 0.09 × 10−4 m s−1. Removal of epicuticular wax by stripping with cellulose acetate or extracting epicuticular plus cuticular wax by dipping
in CHCl3/methanol increased conductance 3.6- and 48.6-fold, respectively. Water fluxes increased with increasing temperature (range
10–39 °C) and energies of activation, calculated for the temperature range from 10 to 30 °C, were 64.8 ± 5.8 and 22.2 ± 5.0 kJ
mol−1 for flux and vapour-concentration-based conductance, respectively.
Received: 23 March 2000 / Accepted: 28 July 2000 相似文献
14.
D'Annibale A Leonardi V Federici E Baldi F Zecchini F Petruccioli M 《Applied microbiology and biotechnology》2007,74(5):1135-1144
Contaminated soil from a historical industrial site and containing sulfide ore ashes and aromatic hydrocarbons underwent sequential
leaching by 0.5 M citrate and microbial treatments. Heavy metals leaching was with the following efficiency scale: Cu (58.7%)
> Pb (55.1%) > Zn (44.5%) > Cd (42.9%) > Cr (26.4%) > Ni (17.7%) > Co (14.0%) > As (12.4%) > Fe (5.3%) > Hg (1.1%) and was
accompanied by concomitant removal of organic contaminants (about 13%). Leached metals were concentrated into an iron gel,
produced during ferric citrate fermentation by the metal-resistant strain BAS-10 of Klebsiella oxytoca. Concomitantly, the acidic leached soil was bioaugmented with Allescheriella sp. DABAC 1, Stachybotrys sp. DABAC 3, Phlebia sp. DABAC 9, Pleurotus pulmonarius CBS 664.97, and Botryosphaeria rhodina DABAC P82. B. rhodina was most effective, leading to a significant depletion of the most abundant contaminants, including 7-H-benz[DE]anthracene-7-one,
9,10-anthracene dione and dichloroaniline isomers, and to a marked detoxification as assessed by the mortality test with the
Collembola Folsomia candida Willem. The overall degradation activities of B. rhodina and P. pulmonarius appeared to be significantly enhanced by the preliminary metal removal. 相似文献
15.
The contribution of ammonia-oxidizing archaea (AOA) to nitrogen removal in wastewater treatment plants (WWTPs) remains unknown.
This study investigated the abundance of archaeal (AOA) and bacterial (ammonia-oxidizing bacteria (AOB)) amoA genes in eight of Bangkok’s municipal WWTPs. AOA amoA genes (3.28 × 107 ± 1.74 × 107–2.23 × 1011 ± 1.92 × 1011 copies l−1 sludge) outnumbered AOB amoA genes in most of the WWTPs even though the plants’ treatment processes, influent and effluent characteristics, removal efficiencies,
and operation varied. An estimation of the ammonia-oxidizing activity of AOA and AOB suggests that AOA involved in autotrophic
ammonia oxidation in the WWTPs. Statistical analysis shows that the numbers of AOA amoA genes correlated negatively to the ammonium levels in effluent wastewater, while no correlation was found between the AOA
amoA gene numbers and the oxygen concentrations in aeration tanks. An analysis of the AOB sequences shows that AOB found in the
WWTPs limited to only two AOB clusters which exhibit high or moderate affinity to ammonia. In contrast to AOB, AOA sequences
of various clusters were retrieved, and they were previously recovered from a variety of environments, such as thermal and
marine environments. 相似文献
16.
Sherri M. Jones Timothy A. Jones Roshni Shukla 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(6):631-638
Short-latency vestibular-evoked potentials to pulsed linear acceleration were characterized in the quail. Responses occurred
within 8 ms following the onset of stimuli and were composed of a series of positive and negative peaks. The latencies and
amplitudes of the first four peaks were quantitatively characterized. Mean latencies at 1.0 g ms−1 ranged from 1265 ± 208 μs (P1, N = 18) to 4802 ± 441 μs (N4, N = 13). Amplitudes ranged from 3.72 ± 1.51 μV (P1/N1, N = 18) to 1.49 ± 0.77 μV (P3/N3, N = 16). Latency-intensity (LI) slopes ranged from −38.7 ± 7.3 μs dB−1 (P1, N = 18) to −71.6 ± 21.9 μs dB−1 (N3, N = 15) and amplitude-intensity (AI) slopes ranged from 0.20 ± 0.08 μV dB−1 (P1/N1, N = 18) to 0.07 ± 0.04 μV dB−1 (P3/N3, N = 11). The mean response threshold across all animals was −21.83 ± 3.34 dB re: 1.0 g ms−1 (N = 18). Responses remained after cochlear extirpation showing that they could not depend critically on cochlear activity.
Responses were eliminated by destruction of the vestibular end organs, thus showing that responses depended critically and
specifically on the vestibular system. The results demonstrate that the responses are vestibular and the findings provide
a scientific basis for using vestibular responses to evaluate vestibular function through ontogeny and senescence in the quail.
Accepted: 18 January 1997 相似文献
17.
Protoplasts were isolated enzymatically from the carrageenophyte red alga Grateloupia turuturu (Halymeniales, Rhodophyta) that occurs along the coast of the French Channel in Normandy. Effects of the main factors on
the protoplast yield were identified to improve the isolation protocol. The optimal enzyme composition for cell wall digestion
and protoplast viability consisted of 2% cellulase Onozuka R-10, 0.5% macerozyme R-10, 2% crude extract from viscera of Haliotis tuberculata, 0.8 M mannitol, 20 mM sodium citrate, 0.3% bovine serum albumin at 25°C, and 4-h incubation period. The protoplasts were
approximately 5–15 μm in diameter, liberated mainly from the surface cell layers. Maximum yield was 1.5 × 107 protoplasts g-1 fresh tissue. The protoplasts underwent initial division after 14 days with a high density level of 1 × 106 cells mL-1 in culture medium and developed into microthalli of a line of two to six cells. 相似文献
18.
A Pseudomonas sp. strain NGK 1 (NCIM 5120) was immobilized in various matrices, namely, alginate, agar (1.8 × 1011 cfu g−1 beads) and polyacrylamide (1.6 × 1011 cfu g−1 beads). The degradation of naphthalene was studied, by freely suspended cells (4 × 1010 cfu ml−1) and immobilized cells in batches, with shaken culture and continuous degradation in a packed-bed reactor. Free cells brought
about the complete degradation of 25 mmol naphthalene after 3 days of incubation, whereas, a maximum of 30 mmol naphthalene
was degraded by the bacteria after 3–4 days of incubation with 50 mmol and 75 mmol naphthalene, and no further degradation
was observed even after 15 days of incubation. Alginate-entrapped cells had degraded 25 mmol naphthalene after 3.5 days of
incubation, whereas agar- and polyacrylamide-entrapped cells took 2.5 days; 50 mmol naphthalene was completely degraded by
the immobilized cells after 6–7 days of incubation. Maximum amounts of 55 mmol, 70 mmol and 67 mmol naphthalene were degraded,
from an initial 75 mmol naphthalene, by the alginate-, agar- and polyacrylamide-entrapped cells after 15 days of incubation.
When the cell concentrations were doubled, 25 mmol and 50 mmol naphthalene were degraded after 2 and 5.5 days of incubation
by the immobilized cells. Complete degradation of 75 mmol naphthalene occurred after 10 days incubation with agar- and polyacrylamide-entrapped␣cells,
whereas only 60 mmol naphthalene was degraded by alginate-entrapped cells after 15 days of␣incubation. Further, with 25 mmol
naphthalene, alginate-, agar- and polyacrylamide-entrapped cells (1.8 × 1011 cfu g−1 beads) could be reused 18, 12 and 23 times respectively. During continuous degradation in a packed-bed reactor, 80 mmol naphthalene
100 ml−1 h−1 was degraded by alginate- and polyacrylamide-entrapped cells whereas 80 mmol naphthalene 125 ml−1␣h−1 was degraded by agar-entrapped cells.
Received: 21 October 1997 / Received revision: 15 January 1998 / Accepted: 18 January 1998 相似文献
19.
Herbert R. L. Drouin 《European biophysics journal : EBJ》1999,28(7):600-604
A new ion-selective liquid membrane microelectrode, based on the neutral carrier 1,1′-bis(2,3-naphtho-18-crown-6), is described
that shows the dependence of EMF on the activity of divalent putrescine cations a
Put, with the linear slope s
Put = 26 ± 3 mV/decade (mean ± SD, N = 18), in the range 10−4–10−1 M at 25 ± 1 °C. Values of potentiometric putrescine cation selectivity coefficients of logK
Pot
Put
j
(mean ± SD, N) are obtained by the separate solution method for the ions K+ (1.0 ± 0.4, 10), Na+ (−1.2 ± 0.4, 8), Ca2+ (−2.3 ± 0.5, 10) and Mg2+ (−2.5 ± 0.5, 7). The microelectrode can be applied for the direct analysis of the activities of free divalent putrescine
cations in the range 5 × 10−4 to 10−1 M in an extracellular ionic environment. Established analytical methods, e.g. high performance liquid chromatography, determine
the total concentration of the derivatives of free and bound putrescine.
Received: 20 December 1998 / Revised version: 7 May 1999 / Accepted: 27 May 1999 相似文献
20.
Thea van de Mortel William Buttemer Peter Hoffman John Hays Andrew Blaustein 《Oecologia》1998,115(3):366-369
Ultraviolet-B (UV-B) irradiation of DNA generates mutagenic photoproducts such as cyclobutane pyrimidine dimers (CPDs) which
can affect the growth and development of amphibian embryos. Differential ability to repair UV-B-induced DNA damage may be␣responsible
for differences in population stability between␣some amphibian species. Photoreactivation via the enzyme photolyase is a major
mechanism used to remove CPDs from DNA. The aim of this study was to determine if photolyase activity differed in three sympatric
Australian amphibian species, one of which has suffered marked population declines (Litoria aurea) and two whose populations do not appear to be in decline (L. dentata and L. peronii). The specific activity of photolyase was measured in each species and compared to the hatching success of their eggs under
unfiltered summer sunlight. The mean specific activities of photolyase were 1.10 ± 0.18 × 1011, 5.76 ± 1.01 × 1011, and 2.66 ± 0.15 × 1011 CPDs repaired per hour per microgram of egg protein extract, for L. aurea, L. dentata and L. peronii, respectively. When intrinsic differences in hatching success between species were controlled for, the relative percentage
hatching success under unfiltered sunlight of L. aurea (77%) was lower than that of L.␣peronii (91%) and L. dentata (98%); however, these values did not differ significantly. L. aurea had the lowest photolyase activity of the three species and showed a non-significant trend of reduced hatching success under
UV-B exposure.
Received: 15 December 1997 / Accepted: 9 March 1998 相似文献