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1.
We evaluated the combined effects of algal (Chlorella vulgaris) food levels (low, 0.5 × 106 (or 2.9 μg C ml−1); and high, 1 × 106 cells ml−1 (or 5.8 μg C ml−1)) and zinc concentrations (0, 0.125, and 0.250 mg l−1 of ZnCl2) on the competition between two common planktonic rotifers Anuraeopsis fissa and Brachionus rubens using their population growth. Median lethal concentration data (LC50) (mean ± 95% confidence intervals) showed that B. rubens was more resistant to zinc (0.554 ± 0.08 mg l−1) than A. fissa (0.315 ± 0.07 mg l−1). A. fissa when grown alone or with Zn was always numerically more abundant than B. rubens. When grown in the absence of zinc, under low- and high-food levels, the peak abundances of A. fissa varied from 251 ± 24 to 661 ± 77 ind. ml−1, respectively, and the corresponding maxima for B. rubens were 52 ± 3 and 102 ± 18 ind. ml−1. At a given food level, competition for food reduced the peak abundances of both rotifers considerably. Increase in Zn concentration
also lowered the rotifer abundances. The impact of zinc on competition between the two-rotifer species was evident at low-food
level, mainly for A. fissa. At zinc concentrations of 0 and 0.125 mg l−1, the populations of both rotifers continued to grow for about 10 days, but thereafter B. rubens began to decline. Role of zinc on the competitive outcome of the two species is discussed in relation to the changing algal
densities in natural water bodies. 相似文献
2.
To screen stimulators from Chinese medicinal insects for mycelial growth and polysaccharides production of Ganoderma lucidum, G. lucidum was inoculated into the media with and without supplementation of medicinal insect extracts. The ethyl acetate extract of
Eupolyphaga sinensis at 55 mg l−1 lead to significant increase in both biomass and intracellular polysaccharides (IPS) concentration from 8.53 ± 0.41 to 14.16 ± 0.43
and 1.28 ± 0.09 to 2.13 ± 0.11 g l−1, respectively. In addition, the ethyl acetate extract of Catharsius molossus at 55 mg l−1 significantly enhanced extracellular polysaccharides (EPS) production; the EPS yield increased from 350.9 ± 14.1 to 475.1 ± 15.3 mg
l−1. There were no new components in the two types of polysaccharides obtained by the addition of the insect extracts. 相似文献
3.
We studied the response of Brachionus patulus to different concentrations of the heavy metal Pb in the presence and absence of sediments. We conducted acute (LC50) and chronic (life table demography and population growth) toxicity tests using sediment levels of 0, 30 and 280 mg l−1 (=0, 17 and 170 NTU) and Pb at 0, 0.06 and 0.6 mg l−1. Experiments were conducted at 20 ± 1°C on a horizontal shaker and algal food (Chlorella vulgaris) was added at a density of 1.0 × 106 cells ml−1. The median lethal concentration (LC50 ± 95% Confidence intervals) of PbCl2 for B. patulus was 6.15 ± 1.08 mg l−1. Age-specific survivorship and fecundity curves showed increase in turbidity level resulted in decreased survival and offspring
production of the rotifers. Increase in Pb concentration too had a negative effect on the survival and reproductive output
of B. patulus. Statistically, average lifespan, life expectancy at birth, gross and net reproductive rates and the rate of population increase
were all significantly influenced by the concentration of Pb, turbidity level as well as the interaction of Pb concentration × turbidity
level. Rotifers exposed to 170 NTU did not grow regardless of the heavy metal concentration in the medium. Similarly, B. patulus exposed to 0.6 mg l−1 Pb did not survive beyond 10 days regardless of the turbidity level in the medium. The rate of population increase of B. patulus derived from the growth experiments was negative in all treatments containing Pb as low as 0.06 mg l−1 or turbidity level as low as 17 NTU. In treatments containing Pb or sediments, there existed no relation between the egg
ratio and the population density.
Guest editors: S. S. S. Sarma, R. D. Gulati, R. L. Wallace, S. Nandini, H. J. Dumont and R. Rico-Martínez
Advances in Rotifer Research 相似文献
4.
The biokinetics of glucose metabolism were evaluated in Aeromonas hydrophila during growth in an anaerobic biosystem. After approx 34 h growth, A. hydrophila metabolized 5,000 mg glucose l−1 into the end-products ethanol, acetate, succinate and formate. The maximum growth rate, μ
m, half saturation coefficients, K
s, microbial yield coefficient, Y, cell mass decay rate coefficient, k
d, and substrate inhibition coefficient, K
si were 0.25 ± 0.03 h−1, 118 ± 31 mg glucose l−1, 0.12 μg DNA mg glucose−1, 0.01 h−1, and 3,108 ± 1,152 mg glucose l−1, respectively. These data were used to predict the performance of a continuous growth system with an influent glucose concentration
of 5,000 mg l−1. Results of the analysis suggest that A. hydrophila will metabolize glucose at greater than 95% efficiency when hydraulic retention times (HRTs) exceed 7 h, whereas the culture
is at risk of washing out at an HRT of 6.7 h. 相似文献
5.
M. Helanto K. Kiviharju T. Granström M. Leisola A. Nyyssölä 《Applied microbiology and biotechnology》2009,83(1):77-83
l-Ribose is a rare and expensive sugar that can be used as a precursor for the production of l-nucleoside analogues, which are used as antiviral drugs. In this work, we describe a novel way of producing l-ribose from the readily available raw material l-arabinose. This was achieved by introducing l-ribose isomerase activity into l-ribulokinase-deficient Escherichia coli UP1110 and Lactobacillus plantarum BPT197 strains. The process for l-ribose production by resting cells was investigated. The initial l-ribose production rates at 39°C and pH 8 were 0.46 ± 0.01 g g−1 h−1 (1.84 ± 0.03 g l−1 h−1) and 0.27 ± 0.01 g g−1 h−1 (1.91 ± 0.1 g l−1 h−1) for E. coli and for L. plantarum, respectively. Conversions were around 20% at their highest in the experiments. Also partially purified protein precipitates
having both l-arabinose isomerase and l-ribose isomerase activity were successfully used for converting l-arabinose to l-ribose. 相似文献
6.
Sanjay Kumar K. Pakshirajan V. Venkata Dasu 《Applied microbiology and biotechnology》2009,84(3):477-486
Glutaminase-free l-asparaginase is known to be an excellent anticancer agent. In the present study, statistically based experimental designs
were applied to maximize the production of glutaminase-free l-asparaginase from Pectobacterium carotovorum MTCC 1428. Nine components of the medium were examined for their significance on the production of l-asparaginase using the Plackett–Burman experimental design. The medium components, viz., glucose, l-asparagine, KH2PO4, and MgSO4·7H2O, were screened based on their high confidence levels (P < 0.04). The optimum levels of glucose, l-asparagine, KH2PO4, and MgSO4·7H2O were found to be 2.076, 5.202, 1.773, and 0.373 g L−1, respectively, using the central composite experimental design. The maximum specific activity of l-asparaginase in the optimized medium was 27.88 U mg−1 of protein, resulting in an overall 8.3-fold increase in the production compared to the unoptimized medium. 相似文献
7.
An effective, simple, and convenient method to improve yeast’s multiple-stress tolerance, and ethanol production was developed.
After an ethanologenic Saccharomyces cerevisiae strain SC521 was treated by nine cycles of freeze-thaw, a mutant FT9-11 strain with higher multiple-stress tolerance was
isolated, whose viabilities under acetic acid, ethanol, freeze-thaw, H2O2, and heat-shock stresses were, respectively, 23-, 26-, 10- and 7-fold more than the parent strain at an initial value 2 × 107 c.f.u. per ml. Ethanol production of FT9-11 was similar (91.5 g ethanol l−1) to SC521 at 30°C with 200 g glucose l−1, and was better than the parent strain at 37°C (72.5 g ethanol l−1), with 300 (111 g ethanol l−1) or with 400 (85 g ethanol l−1) g glucose l−1. 相似文献
8.
T. Zhang 《In vitro cellular & developmental biology. Plant》2007,43(2):91-94
This study investigated the factors affecting in vitro flowering of Perilla frutescens. The shoots regenerated from cotyledonary and hypocotyl explants cultured on Murashige and Skoog (MS) medium supplemented
with benzyladenine (BA) and indole-3-acetic acid, each at 0.5 mg l−1, were excised and transferred to MS medium containing 30 g l−1 of sucrose, 8.25 g l−1 of ammonium nitrate, and 1.0 mg l−1 of BA. After 40 d of culture, 86.2% of shoots flowered and most of which self-fertilized in vitro and produced mature fruits with viable seeds. These seeds were germinated and plants were grown to maturity and flowered
in soil under greenhouse conditions. The in vitro flowering system reported in this study may facilitate rapid breeding of P. frutescens and offers a model system for studying the physiological mechanism of flowering. 相似文献
9.
Octavio Carvajal-Zarrabal Cirilo Nolasco-Hipólito Kopli B. Bujang Ayaaki Ishizaki 《Journal of industrial microbiology & biotechnology》2009,36(3):409-415
A membrane bioreactor for production of nisin Z was constructed using Lactococcus lactis IO-1 in continuous culture using hydrolyzed sago starch as carbon source. A strategy used to enhance the productivity of
nisin Z was to maintain the cells in a continuous growth at high cell concentration. This resulted in a volumetric productivity
of nisin Z, as 50,000 IU l−1 h−1 using a cell concentration of 15 g l−1, 30°C, pH 5.5 and a dilution rate of 1.24 h−1. Adding 10 g l−1 YE and 2 g l−1 polypeptone, other inducers were unnecessary to maintain production of nisin. The operating conditions of the reactor removed
nisin and lactate, thus minimizing their effects which allowed the maintenance of cells in continuous exponential growth phase
mode with high metabolic activity. 相似文献
10.
Sipma J Osuna MB Parshina SN Lettinga G Stams AJ Lens PN 《Applied microbiology and biotechnology》2007,76(2):339-347
Desulfotomaculum carboxydivorans, recently isolated from a full-scale anaerobic wastewater treatment facility, is a sulfate reducer capable of hydrogenogenic
growth on carbon monoxide (CO). In the presence of sulfate, the hydrogen formed is used for sulfate reduction. The organism
grows rapidly at 200 kPa CO, pH 7.0, and 55°C, with a generation time of 100 min, producing nearly equimolar amounts of H2 and CO2 from CO and H2O. The high specific CO conversion rates, exceeding 0.8 mol CO (g protein)−1 h−1, makes this bacterium an interesting candidate for a biological alternative of the currently employed chemical catalytic
water–gas shift reaction to purify synthesis gas (contains mainly H2, CO, and CO2). Furthermore, as D. carboxydivorans is capable of hydrogenotrophic sulfate reduction at partial CO pressures exceeding 100 kPa, it is also a good candidate for
biodesulfurization processes using synthesis gas as electron donor at elevated temperatures, e.g., in biological flue gas
desulfurization. Although high maximal specific sulfate reduction rates (32 mmol (g protein)−1 h−1) can be obtained, its sulfide tolerance is rather low and pH dependent, i.e., maximally 9 and 5 mM sulfide at pH 7.2 and
pH 6.5, respectively. 相似文献
11.
Supplementation with CaCl2·2H2O (50 mg l−1) or CuSO4·5H2O (10 mg l−1) improved mannitol production by Candida magnoliae by 14.5 and 18.6% (25 and 32 g/L), respectively. When used in combination, they acted synergistically: Ca2+ decreased the intracellular concentration of mannitol 30%, whereas Cu2+ increased the intracellular activity of mannitol dehydrogenase 1.6-times more than control. Ca2+ probably works by altering the permeability of cells to mannitol, whereas, Cu2+ increases the activity of an enzyme responsible for mannitol biosynthesis. 相似文献
12.
Balk M Weijma J Goorissen HP Ronteltap M Hansen TA Stams AJ 《Applied microbiology and biotechnology》2007,73(5):1203-1211
A sulfate-reducing bacterium, strain WW1, was isolated from a thermophilic bioreactor operated at 65°C with methanol as sole
energy source in the presence of sulfate. Growth of strain WW1 on methanol or acetate was inhibited at a sulfide concentration
of 200 mg l−1, while on H2/CO2, no apparent inhibition occurred up to a concentration of 500 mg l−1. When strain WW1 was co-cultured under the same conditions with the methanol-utilizing, non-sulfate-reducing bacteria, Thermotoga lettingae and Moorella mulderi, both originating from the same bioreactor, growth and sulfide formation were observed up to 430 mg l−1. These results indicated that in the co-cultures, a major part of the electron flow was directed from methanol via H2/CO2 to the reduction of sulfate to sulfide. Besides methanol, acetate, and hydrogen, strain WW1 was also able to use formate,
malate, fumarate, propionate, succinate, butyrate, ethanol, propanol, butanol, isobutanol, with concomitant reduction of sulfate
to sulfide. In the absence of sulfate, strain WW1 grew only on pyruvate and lactate. On the basis of 16S rRNA analysis, strain
WW1 was most closely related to Desulfotomaculum thermocisternum and Desulfotomaculum australicum. However, physiological properties of strain WW1 differed in some aspects from those of the two related bacteria. 相似文献
13.
14.
Four temperature treatments were studied in the climate controlled growth chambers of the Georgia Envirotron: 25/20, 30/25,
35/30, and 40/35 °C during 14/10 h light/dark cycle. For the first growth stage (V3-5), the highest net photosynthetic rate
(P
N) of sweet corn was found for the lowest temperature of 28–34 μmol m−2 s−1 while the P
N for the highest temperature treatment was 50–60 % lower. We detected a gradual decline of about 1 P
N unit per 1 °C increase in temperature. Maximum transpiration rate (E) fluctuated between 0.36 and 0.54 mm h−1 (≈5.0–6.5 mm d−1) for the high temperature treatment and the minimum E fluctuated between 0.25 and 0.36 mm h−1 (≈3.5–5.0 mm d−1) for the low temperature treatment. Cumulative CO2 fixation of the 40/35 °C treatment was 33.7 g m−2 d−1 and it increased by about 50 % as temperature declined. The corresponding water use efficiency (WUE) decreased from 14 to
5 g(CO2) kg−1(H2O) for the lowest and highest temperature treatments, respectively. Three main factors affected WUE, P
N, and E of Zea: the high temperature which reduced P
N, vapor pressure deficit (VPD) that was directly related to E but did not affect P
N, and quasi stem conductance (QC) that was directly related to P
N but did not affect E. As a result, WUE of the 25/20 °C temperature treatment was almost three times larger than that of 40/35 °C temperature treatment. 相似文献
15.
Ling Zhao Yongming Bao Jingyun Wang Boshi Liu Lijia An 《World journal of microbiology & biotechnology》2009,25(1):57-64
A mutant designated as UV-3 was obtained from wild-type Enterobacter aerogenes 10293 through u.v. radiation. The activities of α-acetolactate decarboxylase (Ald), lactate dehydrogenase (Ldh) and diacetyl
reductase (Dr) in UV-3 were strongly attenuated, with the lowest activities at pH 7.0–7.5, and temperature between 36 and
39°C. Compared to the wild-type, the yield of diacetyl by UV-3 was increased 18.7-fold, up to 1.05 ± 0.01 g l−1. Acetoin and ethanol productions were decreased by 48.4 and 71.4%, respectively, but acetate yield was increased by 34.6%.
Optimum medium for diacetyl production by UV-3 contained 10% glucose, 0.5% peptone, 0.5% yeast extract powder, 0.01% (NH4)2SO4, 0.1% citric acid, 0.2% MnSO4 and 0.2% MgSO4, and this was determined by one-factor-at-a-time approach. Data from the five level central composite designs demonstrated
that initial pH of 7.0, temperature of 37°C and rotational speed of 180 rev/min were optimum processing parameters for diacetyl
production. The maximum yield of diacetyl could reach 1.35 g l−1 in a 5-l bioreactor. These results showed an enhancement of the non-enzymatic oxidative decarboxylation of α-acetolactate
and a decrease in the activities of Ald, Ldh and Dr as a consequence of diacetyl accumulation in UV-3. 相似文献
16.
Cyanobacteria blooms (especially Microcystis spp.) are thought to alter dominance of large-sized daphnids into small-sized metazoan zooplankton. However, several field
investigations show different phenomena. Laboratory experiments were conducted based on the hypothesis that different Microcystis spp. concentrations would influence competitive outcomes using two algal combinations of different concentrations and four
species of cladocerans. In the algal combination of 50 mg l−1 colonial Microcystis spp. + 1 mg l−1
Scenedesmus obliquus (fresh weight), Daphnia carinata was absent during the experiment in competition with other cladocerans. Decreasing colonial Microcystis spp. concentration (10 mg l−1) resulted in a shift from dominance by small-sized cladocerans to dominance by D. carinata. No significant effects of different concentrations of colonial Microcystis spp. on competitive outcomes were shown among three small-sized cladocerans. These results support the idea that cyanobacteria
concentration affects the dominance status of large-bodied daphnid. 相似文献
17.
Corynebacterium acetoacidophilum RYU3161 was cultivated in al-histidine-limited fed-batch culture. To investigate the effect of cell growth on thel-proline production, 5l fed-batch culture was performed using an exponential feeding rate to obtain the specific growth rates (μ) of 0.04, 0.06,
0.08, and 0.1 h−1. The results show that the highest production ofl-proline was obtained at μ=0.04 h−1. The specificl-proline production rate (Qp) increased proportionally as a function of the specific growth rate, but decreased after it revealed the maximum value at
μ=0.08 h−1. Thus, the highest productivity ofl-proline was 1.66 g L−1 h−1 at μ=0.08 h−1. The results show that the production of L-proline inC. acetoacidophilum RYU3161 has mixed growth-associated characteristics. 相似文献
18.
Chu WH 《Journal of industrial microbiology & biotechnology》2007,34(3):241-245
Thirty-five strains capable of secreting extracellular alkaline proteases were isolated from the soil and waste water near
the milk processing plant, slaughterhouse. Strain APP1 with the highest-yield alkaline proteases was identified as Bacillus sp. The cultural conditions were optimized for maximum enzyme production. When the initial pH of the medium was 9.0, the
culture maintained maximum proteolytic activity for 2,560 U ml−1 at 50°C for 48 h under the optimized conditions containing (g−1): soyabean meal, 15; wheat flour, 30; K2HPO4, 4; Na2HPO4, 1; MgSO4·7H2O, 0.1; Na2CO3, 6. The alkaline protease showed extreme stability toward SDS and oxidizing agents, which retained its activity above 73
and 110% on treatment for 72 h with 5% SDS and 5% H2O2, respectively. 相似文献
19.
Aguedo M Gomes N Garcia EE Waché Y Mota M Teixeira JA Belo I 《Biotechnology letters》2005,27(20):1617-1621
Yarrowia lipolytica converts methyl ricinoleate to γ-decalactone, a high-value fruity aroma compound. The highest amount of 3-hydroxy-γ-decalactone
produced by the yeast (263 mg l-1) occurred by increasing the kLa up to 120 h−1 at atmospheric pressure; above it, its concentration decreased, suggesting a predominance of the activity of 3-hydroxyacyl-CoA
dehydrogenase. Cultures were grown under high-pressure, i.e., under increased O2 solubility, but, although growth was accelerated, γ-decalactone production decreased. However, by applying 0.5 MPa during
growth and biotransformation gave increased concentrations of dec−2-en-4-olide and dec-3-en-4-olide (70 mg l−1). 相似文献
20.
The rpiB gene, encoding ribose-5-phosphate isomerase (RpiB) from Clostridium thermocellum, was cloned and expressed in Escherichia coli. RpiB converted d-psicose into d-allose but it did not convert d-xylose, l-rhamnose, d-altrose or d-galactose. The production of d-allose by RpiB was maximal at pH 7.5 and 65°C for 30 min. The half-lives of the enzyme at 50°C and 65°C were 96 h and 4.7 h,
respectively. Under stable conditions of pH 7.5 and 50°C, 165 g d-allose l−1
was produced without by-products from 500 g d-psicose l−1 after 6 h. 相似文献